Exploiting limitations of fused deposition modeling to enhance mixing in 3D printed microfluidic devices

Purpose The purpose of this study is to introduce an alternative construction for microfluidic micromixers, where the effect of the extruded filaments in the fused deposition modeling (FDM) technique is used to enhance mixing performance identified as a challenge in microfluidic micromixers. Design/methodology/approach A simple Y-shaped micromixer was designed and printed using FDM technique. Experimental and numerical studies were conducted to investigate the effect of the extruded filaments on the flow behavior. The effects of the extruded width (LW), distance between adjacent filaments (b) and filament height (h1) are investigated on the mixing performance and enhancing mixing in the fabricated devices. The performance of fabricated devices in mixing two solutions was tested at flow rates of 5, 10, 20, 40, 80 and 150 µL/min. Findings The experimental results showed that the presence of geometrical features on microchannels, because of the nature of the FDM process, can act as ridges and generate a lateral transform through the transverse movement of fluids along the groove. The results showed the effect of increasing ridge height on the transverse movement of the fluids and, therefore, chaotic mixing over the ridges. In contrast, in the shallow ridge, diffusion is the only mechanism for mixing, which confirms the numerical results. Originality/value The study presents an exciting aspect of FDM for fabrication of micromixers and enhance mixing process. In comparison to other methods, no complexity was added in fabrication process and the ridges are an inherent property of the FDM process.

Implications of virtual CBCT-based immediate implant planning for maxillary and mandibular first molars

The purpose of his study was to investigate the projected ridge-implant dimensions derived from virtual superimposition of implants on intact first molars mimicking immediate implantation in the mandible (Md1) and maxilla (Mx1) using cone-beam computed tomography (CBCT). The CBCT records of 41 patients (19 males and 22 females) with Md1 or Mx1 were collected. 10 mm-long cylindrical implants with different diameters were virtually positioned at prosthetically ideal angles into interradicular septum using CBCT software. Radiographic alveolar ridge height (ARH), alveolar ridge width (ARW), gap distance, and vertical distance from the implant platform to the alveolar crest were measured. Twenty Mx1s (48.8%) and 21 Md1s (51.2%) were included. The mean ARH values were 7.13 ± 4.32 mm and 15.64 ± 1.80 mm for Mx1 and Md1, respectively. 87.8% of mesiobuccal sites had gap distance > 2 mm when 6 mm diameter implants were used. Increasing implant diameter from 6 mm to 9 mm decreased the percentage of sites with ARW > 2 mm from 80.5% to 41.5% buccally and from 86.4% to 26.8% lingually. The mean vertical distance from the implant platform to the alveolar crest was 1.41 ± 1.09 mm buccally and 1.11 ± 1.10 mm lingually. Immediate implant placement of first molars, especially in the maxilla, requires stringent presurgical evaluation. Implants no wider than 6 mm placed into the interradicular septum may meet acceptable running room and alveolar plate thickness criteria if the jumping distance is grafted and further clinical trials are needed to confirm these findings in this virtual study

Springtail coloration at a finer scale: mechanisms behind vibrant collembolan metallic colours

The mechanisms and evolution of metallic structural colours are of both fundamental and applied interest, yet most work in arthropods has focused on derived butterflies and beetles with distinct hues. In particular, basal hexapods—groups with many scaled, metallic representatives—are currently poorly studied and controversial, with some recent studies suggesting either that thin-film (lamina thickness) or diffraction grating (longitudinal ridges, cross-ribs) elements produce these colours in early Lepidoptera and one springtail (Collembola) species. Especially the collembolan basal scale design, consisting of a single lamina and longitudinal ridges with smooth valleys lacking cross-ribs, makes them an interesting group to explore the mechanisms of metallic coloration. Using microspectroscopy, Raman spectroscopy, electron microscopy and finite-difference time-domain optical modelling, we investigated scale colour in seven springtail species that show clear metallic coloration. Reflectance spectra are largely uniform and exhibit a broadband metallic/golden coloration with peaks in the violet/blue region. Our simulations confirm the role of the longitudinal ridges, working in conjunction with thin-film effects to produce a broadband metallic coloration. Broadband coloration occurs through spatial colour mixing, which probably results from nanoscale variation in scale thickness and ridge height and distance. These results provide crucial insights into the colour production mechanisms in a basal scale design and highlight the need for further investigation of scaled, basal arthropods.

Agrotechnical and Energy Performance of Tillage Tools

Introduction. One of the areas of agricultural production is crop production. At the same time, it is necessary to take into account all available possibilities of reducing the energy consumption and labor required for tillage operations that can be achieved by using energy efficient tillage tools. Materials and Methods. In the course of the research, an agrotechnical and energy assessment of the technological process of soil cultivation performed by tillage tools was carried out. The agrotechnical assessment includes identifying the indicators of unevenness of the tillage tool travel depth, soil pulverization, ridging, and the content of erosion threatening particles. As an energy assessment, the indicator of draught created by a tillage tool was taken. The researches were carried out for various configurations of the chisel cultivators with flat and curved hoes, and elements made of polymer. Results. The data of agricultural assessment and draught of chisel cultivators were obtained for various agricultural backgrounds: winter wheat stubble with preliminary disking in one track, winter barley stubble with preliminary disking in one track, and autumn fallow on the background. Discussion and Conclusion. According to the results of the research, it was found that, in terms of quality indicators, the tillage tools meet the agrotechnical requirements for a given processing depth of 25–35 cm. The operation of the chisel equipped with a curved hoe is characterized by the highest presence of clods up to 5 cm (91–96%). The ridge height was 6.8–8.0 cm for all tillage tools. It has been established that the tillage tools are advisable to be uses for anti-erosion soil cultivation. In terms of preserving plant and crop residues, a chisel with a curved hoe providing their content by 9.5–28.6% more than with a polymer of 13.2–14.3%. The chisel with polymer has the smallest draught of 7.6 kN, which is 18.28% lower in comparison with tillage tools equipped with a flat hoe.

Effect of Ridge Height, Row Grade, and Field Slope on Nutrient Losses in Runoff in Contour Ridge Systems under Seepage with Rainfall Condition

Seepage plays a key role in nutrient loss and easily occurs in widely-used contour ridge systems due to the ponding process. However, the characteristics of nutrient loss and its influential factors under seepage with rainfall condition in contour ridge systems are still unclear. In this study, 23 seepage and rainfall simulation experiments are arranged in an orthogonal rotatable central composite design to investigate the role of ridge height, row grade, and field slope on Nitrate (NO3−–N) and Orthophosphate (PO4+3–P) losses resulting from seepage in contour ridge systems. In total, three types of NO3−–N and PO4+3–P loss were observed according to erosion processes of inter-rill–headward, inter-rill–headward–contour failure, and inter-rill–headward–contour failure–rill. Our results demonstrated that second-order polynomial regression models were obtained to predict NO3−–N and PO4+3–P loss with the independent variables of ridge height, row grade, and field slope. Ridge height was the most important factor for nutrient loss, with a significantly positive effect and the greatest contribution (52.35–53.47%). The secondary factor of row grade exerted a significant and negative effect, and was with a contribution of 19.86–24.11% to nutrient loss. The interaction between ridge height and row grade revealed a significantly negative effect on NO3−–N loss, whereas interactions among the three factors did not significantly affect PO4+3–P loss. Field slope only significantly affected NO3−–N loss. The optimal design of a contour ridge system to control nutrient loss was obtained at ridge height of 8 cm, row grade of 2°, and field slope of 6.5°. This study provides a method to assess and model nutrient loss, and improves guidance to implement contour ridge systems in terms of nutrient loss control.

The volumetric evaluation of sinüs floor augmentation using platelet rich-fibrin and allogenic bone graft mixture with simultaneous dental implant placement in severely atrophic posterior maxilla

Objectives: To evaluate the efficacy of the combination of platelet-rich fibrin (PRF) and mineralized bone allograft on the volume of the new bone formation in the sinus floor augmentation of the severely atrophic residual alveolar crest with simultaneous dental implant placement. Materials and Methods: All clinical and radiological data of patients treated with sinus floor augmentation using the combination of PRF and demineralized bone allograft with simultaneous dental implant placement between 01/04/2013 and 01/03/2020 were retrieved from the archives. The main inclusion criterion for the study was a residual ridge height less than 2 mm. The volume of the maxillary sinus cavity was measured by a software program on pre-operative and post-operative cone beam computerized tomography (CBCT) sections. The graft volume was calculated by subtracting pre-operative and post-operative total sinus volume. Residual and post-operative ridge heights were measured by the software program on the mid-coronal and mid-sagittal sections of pre-operative and post-operative CBCT images. Results: Eighteen patients with 26 sinus augmentations were included in the study. Forty-six dental implants were placed simultaneously with sinus floor augmentation. The follow-up periods of cases varied between 19 and 29 months. All cases showed new bone regeneration on axial, coronal and sagittal sections of post-operative CBCT data. The mean volume of newly regenerated bone was calculated as 2.1(±0.9) ml. Post-operative ridge heights was significantly increased compared to pre-operative residual ridge heights (p<0.05). There was no sign of a relationship between residual and post-operative ridge heights (p>0.05). Conclusion: The PRF and demineralized bone allograft combination used in sinus floor augmentation may provide healthy new bone that supports simultaneously placed dental implants in function in the severely atrophic alveolar crests with a residual ridge height less than 2 mm. Keywords: Sinüs floor augmentation ; allograft ; cone-beam computed tomography ; dental implant

Influence of flow hydraulic characteristics on the ridge lower escarpment angle

In the riverbeds and canals that run on non-cohesive grounds, bedload sediments move in the ridges form. Ridge forms determine the flow rate of bedload sediments, hydraulic resistances, the types and rates of deformations in alluvial channels. The main elements of ridge formations are height, gentle and steep length with corresponding escarpments. The ridge's steep length and this corresponding escarpment change with changes in the flow hydraulic characteristics. With a change in the ridge's steep length and its steep escarpment, the hydraulic resistance of the channel, the flow rate of bedload sediments, the types, and the channel deformation rates change. In the laboratory, a series of experiments with different sediments compositions and diameters were carried out on the hydraulic tray to determine the main elements (total, gentle and steep length, and the ridge height) and the dynamic characteristics of the ridge formations and the flow hydraulic characteristics. Calculation formulas for determining the coefficient of the ridge lower escarpments with and without taking into account the angle of the natural ground escarpment under water and in the dry state, and the dependence of the steepness of the relative ridge on the relative flow velocity, are obtained. The obtained dependencies allow to accurately determine the geometric and dynamic characteristics of bedload ridges and the corresponding hydraulic characteristics that may define the view ridge formations, ridges resistance of the channel, and the flow rate of bedload sediments, and to design sustainable escarpments large channels.