Macroscopic Grooves Research Articles

Improving air-water two-phase flow pumping in centrifugal pumps using novel grooved front shrouds

The present investigations aim to improve the gas-liquid two-phase transport in centrifugal pumps using a novel front shroud design with macroscopic grooves. This increases the secondary flow strength and the two-phase mixing, boosting the performance. A total of 23 different circumferential and radial groove profiles were numerically investigated to identify the best configuration leading to the highest mixing efficiency. Three different loads were considered, i.e., part load, optimal point, and overload. Additionally, the performance of the novel designs was compared with that of the established alternatives, involving two different clearance gaps and/or an inducer. While circumferential grooves already lead to a slightly improved specific delivery work, radial grooves improve noticeably the pump efficiency and deliver a very high two-phase mixing compared to other traditional pump configurations. Under conditions of optimal loading, the utilization of circumferential grooves led to a phase mixing enhancement of approximately 19.5%, whereas the implementation of radial grooves exhibited a notable improvement in mixing efficiency by 64.8% compared to the standard gap. The radial design R14 is superior to all other designs regarding efficiency and phase mixing. It is therefore recommended for transporting gas-liquid two-phase flows.

Development of Mixed Flow Fans with Bio-Inspired Grooves.

Mixed flow fan is a kind of widely used turbomachine, which has faced problems of further performance improvement in traditional design methods in recent decades. Inspired by the microgrooves such as riblets and denticles on bird feathers and shark skins, we here propose biomimetic designs of various blades with the bio-inspired grooves, aiming at the improvement of the aeroacoustic performance. Based on a systematic study with computational fluid dynamic analyses, we found that these designs had the potential in noise suppression even with macroscopic grooves. Our best design can suppress turbulence kinetic energy by approximately 38% at the blade leading edge with aerodynamic efficiency loss of only 0.3 percentage points. This improvement is achieved by passive flow control. The vortical structures are changed in a favorable way at the leading edge due to the grooves. We believe that these biomimetic designs could provide a promising future of enhancing the performance of mixed flow fans by making grooves of ideal flow passages on the suction faces of blades in accord with the theory of pump design.

Guided droplet transport on synthetic slippery surfaces inspired by a pitcher plant

We show how anisotropic, grooved features facilitate the trapping and directed transport of droplets on lubricated, liquid-shedding surfaces. Capillary action pins droplets to topographic surface features, enabling transport along the feature while inhibiting motion across (or detachment from) the feature. We demonstrate the robustness of this capillary-based mechanism for directed droplet transport on slippery surfaces by combining experiments on synthetic, lubricant-infused surfaces with observations on the natural trapping surface of a carnivorous pitcher plant. Controlling liquid navigation on synthetic surfaces promises to unlock significant potential in droplet-based technologies. Our observations also offer novel insight into the evolution of the Nepenthes pitcher plant, indicating that the 'pitfall' trapping mechanism is enhanced by the lubricant-infused, macroscopic grooves on the slippery peristome surface, which guide prey into the trap in a way that is more tightly controlled than previously considered.

Effect of Macroscopic Grooves on Bone Formation and Osteoblastic Differentiation.

The aim of this study is to investigate the effect of macroscopic grooves on bone formation in vivo and differentiation of human mesenchymal stem cells (hMSCs) in vitro. The effects of macroscopic grooves on titanium alloy implants and disks were tested in rabbit tibiae and cultured hMSCs. The bone-to-implant contact (BIC) and bone area were evaluated in rabbit tibiae at 6 and 24 weeks after implant insertion. Osteoblastic differentiation was assessed by alkaline phosphatase (ALP) activity and real-time reverse-transcription polymerase chain reaction (RT-PCR) on days 7, 14, and 21. All values were statically analyzed. BIC and bone area inside the grooves were significantly higher than those of control implants (P < 0.05). ALP activity was significantly higher for titanium disks with macroscopic grooves than without grooves on day 14 (P < 0.05). Real-time RT-PCR showed that the expression of osteogenic genes was significantly higher for disks with grooves on day 7 (P < 0.01). Macroscopic grooves accelerate osteoblastic differentiation in vitro and stimulate direct bone growth and deposition within the grooves in vivo.

The influence of surface modification on bacterial adhesion to titanium-based substrates.

This study examines bacterial adhesion on titanium-substrates used for bone implants. Adhesion is the most critical phase of bacterial colonization on medical devices. The surface of titanium was modified by hydrothermal treatment (HT) to synthesize nanostructured TiO2-anatase coatings, which were previously proven to improve corrosion resistance, affect the plasma protein adsorption, and enhance osteogenesis. The affinity of the anatase coatings toward bacterial attachment was studied by using a green fluorescent protein-expressing Escherichia coli (gfp-E. coli) strain in connection with surface photoactivation by UV irradiation. We also analyzed the effects of surface topography, roughness, charge, and wettability. The results suggested the dominant effects of the macroscopic surface topography, as well as microasperity at the surface roughness scale, which were produced during titanium machining, HT treatment, or both. Macroscopic grooves provided a preferential site for bacteria deposit within the valleys, while the microscopic roughness of the valleys determined the actual interaction surface between bacterium and substrate, resulting in an "interlocking" effect and undesired high bacterial adhesion on nontreated titanium. In the case of TiO2-coated samples, the nanocrystals reduced the width between the microasperities and thus added nanoroughness features. These factors decreased the contact area between the bacterium and the coating, with consequent lower bacterial adhesion (up to 50% less) in comparison to the nontreated titanium. On the other hand, the pronounced hydrophilicity of one of the HT-coated discs after pre-irradiation seemed to enhance the attachment of bacteria, although the increase was not statistically significant (p > 0.05). This observation may be explained by the acquired similar degree of wetting between gfp-E. coli and the coating. No correlation was found between the bacterial adhesion and the ζ-values of the samples in PBS, so the effect of surface charge was considered negligible in this study.

Hyperbolic-metamaterial antennas for broadband enhancement of dipole emission to free space

Dipole emitters used in nano optics and nanophotonics (e.g., fluorescent molecules or quantum dots) are weak radiators and thus detecting the radiation of a single emitter gets possible only if it is significantly enhanced. For this enhancement, one often utilizes resonant nanoantennas (Purcell's effect); this method, however, requires the exact knowledge of source location and radiation frequency which constitute a significant drawback. One known possibility for broadband location-insensitive radiation enhancement is to use a layer of the so-called hyperbolic metamaterial. However, the enhanced radiated energy is mainly directed into the volume of the lossy medium, where it is lost to heating. In this work, we suggest specific shapes of macroscopic hyperbolic metamaterial samples to open radiation windows for enhanced radiation to free space. We show that hyperbolic media slabs with properly shaped macroscopic grooves convert the evanescent waves produced by a dipole into waves traveling in free space, which results in the enhancement of useful radiation by one to two orders of magnitude. That level of enhancement of radiation into free-space which is also wideband and of non-resonant nature has not been reported up to now. These results may open possibilities for realization of broadband and directive antennas, where the primary radiators are randomly positioned fluorescent molecules or quantum dots.

Preparation, characterization, in vitro bioactivity, and osteoblast adhesion of multi‐level porous titania layer on titanium by two‐step anodization treatment

To combine the advantages of different electrolytes in anodic oxidation, pure titanium samples were anodized in CH(3) COOH electrolyte according to a novel anodizing treatment regime and then in H(2) SO(4) electrolyte in potentialstatic mode. The in vitro bioactivity of the as-prepared titanium samples was evaluated by simulated body fluid (SBF) test. In addition, MG63 osteoblast-like cells were cultured on surfaces of the as-prepared titanium samples to evaluate osteoblast adhesion ability. The titanium samples after the two-step anodization treatment were covered by titania layers of anatase and/or rutile with several micrometres thickness and presented a multi-level porous surface morphology consisting of interlaced grooves about 20-μm wide overlaid with submicron scale pores. The SBF test results showed that the crystal titania layers prepared at appropriate conditions were able to induce apatite-forming in 7 days, indicating that the abundance of surface Ti-OH groups and (101)-oriented rutile structure both played important roles in in vitro bioactivity of titania layers. The cell experiment results showed that the macroscopic grooves could effectively promote osteoblast adhesion and growth and submicron scale pores might be beneficial to osteoblast adhesion. The two-step anodization treatment might be a promising candidate for surface modification of titanium implant.

Effect of a macroscopic groove on bone response and implant stability

The aim of this study was to investigate the effect of a macroscopic groove on bone response and implant stability during the early stages of healing using a rabbit tibia model. Anodized titanium implants with (n=24) and without (n=24) macroscopic grooves were prepared. A total of 12 rabbits were used and each received four implants: six rabbits with implants with macroscopic grooves (test group) and six rabbits with implants without macroscopic groves (control group). Histomorphometry, resonance frequency, and removal torque value were evaluated 2 and 6 weeks post-implant-insertion. At 2 and 6 weeks, there was no significant difference between the two groups in the percentage of bone-to-implant contact (P>0.05). At 6 weeks, the test group had significantly higher implant stability quotient values than the control group (P<0.05). At 2 and 6 weeks, implants with grooves showed a significantly greater resistance to reverse torque than control implants (P<0.05). The groove on the oxidized titanium surface may increase both resistance to shear load and adhesion at the bone-implant interface. A geometric feature such as a macroscopic groove may facilitate osseointegration and increase implant stability in various clinical conditions. Further studies are required to confirm whether the improvement in implant stability will enhance treatment success in humans.

Stimulation of Directed Bone Growth at Oxidized Titanium Implants by Macroscopic Grooves: An In Vivo Study

The influence of thread design at the millimeter level and surface topography at the micrometer level on bone integration and the stability of dental implants have been studied extensively. However, less is known about the influence of implant structures in the range of 50 to 200 microm. The present in vivo investigation was undertaken to study if bone formation and implant stability were influenced by 110 (S1) and 200 (S3) microm-wide and 70 microm-deep grooves positioned at a thread flank of oxidized titanium implants. Eighteen rabbits and oxidized titanium implants (3.75 mm in diameter and 7 mm long) were used in the study. Nine rabbits received three control implants and three test implants with a 110 microm-wide groove added to one thread flank. The remaining nine rabbits received three control implants and three test implants with a 200 microm-wide groove. The animals were followed for 6 weeks. Removal torque (RTQ) tests were applied to two of the implants in each leg. The remaining implant per leg was retrieved for histology. The degree of bone fill within the grooves and corresponding bone formation at the opposing surfaces, the bone area within the threads, and the degree of bone-implant contact were calculated for each implant. The histologic analyses revealed an affinity for bone formation within the grooves. The RTQ tests showed that the peak RTQ was approximately 30% higher for the S1 implants compared with control implants without a groove. The difference was statistically significant (p < .05) for tibial and pooled implants. A similar but smaller and not statistically significant effect, approximately 8%, was measured for the S3 implants. The histomorphometric measurements confirmed the observed affinity of bone for the grooves. For S1 implants, 78.7 +/- 15.8% of the grooves were filled with bone, whereas only 46.2 +/- 27% of the corresponding flank surface showed the presence of bone (p < .05). The corresponding figures for S3 and control implants were 72.7 +/- 25.1% and 48.5 +/- 13.6%, respectively (p < .05). The degrees of bone-implant contact and bone area within the threads were similar for test and control implants. It is concluded that 110 and 200 microm-wide and 70 microm-deep grooves at oxidized implant surfaces stimulated bone to preferentially form within and along the groove in the rabbit model. The 110 microm-wide groove was shown to increase the resistance to shear forces significantly. It is suggested that implants with such a groove may be one way to optimize implant stability in suboptimal clinical conditions.

Effect of pre-amorphization of polycrystalline silicon on agglomeration of TiSi2 in subquarter micron Si lines

We investigated the effect of C49-to-C54 conversion behavior on the agglomeration of Ti-silicide fabricated on subquarter micron polycrystalline Si lines by comparing pre-amorphized samples with conventional ones. Pre-amorphization of polycrystalline Si enhances the C49-to-C54 transformation on subquarter micron linewidths, however, it results in the early development of macroscopic grooves during the second rapid thermal annealing. From these results, we suggest the existence of an extra thermal budget during the second rapid thermal annealing of the pre-amorphized samples, which deteriorates the thermal stability of the C54-TiSi2 featured line. It is also shown that C49-to-C54 transformation on a 0.2 μm linewidth in the conventional samples has two kinds of competing factors when postannealing is added. One is the tendency of C54 transformation and the other is agglomeration of C49-TiSi2 grains. During high temperature annealing (&amp;gt;850 °C), C49-TiSi2 has been agglomerated by a thinning mechanism instead of transformation into the C54 phase.

Experimental Fibromuscular Arterial Dysplasia

Fibromuscular dysplasia is being diagnosed more frequently because of a common use of renal arteriography in the evaluation of hypertension. The etiology of this almost unique condition is unknown, although the clinical and pathological associations of the varying subgroups have been elucidated (1, 2). In an effort to explain the high incidence of the disease in women with ptotic kidneys and the prominent change in appearance (3) that the upright position produces in fibromuscular lesions, an investigation to assess the long-term effect of stretching of the renal artery is in progress. Materials and Methods Twelve dogs have been studied and 17 arteries have been stretched at this time. In addition, one control experiment in which the kidney pedicle was mobilized without extensive dissection but not retained at a lower position was conducted. Base-line aortography was performed by percutaneous puncture in all cases, and subsequently the kidney was tethered in the iliac fossa by retaining sutures between the capsule and the posterior abdominal wall. In one case fixation has been by means of a Silastic device which has overlapped the renal pedicle and has prevented the mobilized kidney from returning to its original position. Aortography was then performed at varying times in the stretching period. Histopathologic examination of the renal artery has been carried out at autopsy, with special emphasis on the areas of irregular arteriographic appearances. Where excessive stretching could be provided with angulation of the renal artery from its cranial direction to an almost parallel situation beside the abdominal aorta, arteriographic changes as shown in Figures 1 and 2 could be produced in each animal. In some of these dogs the retention mechanism later proved ineffective, but where it remained the angiographic appearances persisted. Of the 12 animals studied thus far, only 3 fit into this latter category. The downward rotation of the renal artery that was necessary in the successful cases was never less than 130 range of angulation. The pathological appearances corresponding to the angiograms shown demonstrate prominent macroscopic grooves on the surface of the renal artery, together with collagenous thickening in the deeper intima and media (Fig. 3). With special staining, rupture of the internal elastic membrane, together with fragmentation of the elastic fibers in the media, was demonstrated. Subsequent experiments in different animals have indicated that the critical factor in the development of the lesion has been the extent of stretching of the artery. Where only slight angulation is produced, irregular changes that could be attributed possibly to extramural dissection were noted as these subsequently resolved. In both the control experiment and in those in which the kidney was tethered by Silastic material these early changes did not occur.