Natural Frequencies of Diatom Shells: Alteration of Eigenfrequencies Using Structural Patterns Inspired by Diatoms

Diatoms have delicate and complex shells showing different lightweight design principles that have already been applied to technical products improving the mechanical properties. In addition, diatom inspired structures are expected to significantly affect the vibration characteristics, i.e., the eigenfrequencies. Directed eigenfrequency shifts are of great interest for many technical applications to prevent undesired high vibration amplitudes. Therefore, numerous complex diatom inspired dome structures primarily based on combs, ribs, and bulging patterns were constructed and their eigenfrequencies were numerically studied. Different structural patterns were identified to significantly affect eigenfrequencies. The results were compared to dome structures equipped with rib patterns in combination with a common structural optimization tool. The study indicates that a combination of (1) selecting diatom inspired structural patterns that strongly affect eigenfrequencies, and (2) adapting them to the boundary conditions of the technical problem is an efficient method to design diatom inspired lightweight solutions with high eigenfrequencies.

Comparative Effectiveness of Epidural Steroid İnjections in Patients With Disc Bulging and Disc Protrusion

Purpose Discogenic low back pain is a widespread disorder in the world. Many methods have been developed and continue to be developed in the treatment of discogenic low back pain. We aimed to examine the effect of epidural steroid administration on disc bulging and disc protrusion in patients with discogenic low back pain. Design The clinical effects of interlaminar epidural steroids administered to 71 patients who were admitted to our clinic and whose treatment did not require surgery were radiologically divided into two groups disc bulging and disc protrusion. Patients were followed up for six months and clinical results were recorded. Methods The scores of the Visual Analog Scale (VAS) and Oswestry Disability Index (ODI) were measured before the procedure, one week after the procedure, one month after the procedure, and six months after the procedure. The normal distribution of continuous variables was evaluated using the Kolmogorov-Smirnov test. Continuous variables were compared with the Mann-Whitney U test and categorical variables were compared using the Chi-square test or Fisher's exact test. Results There was no significant difference in demographic data in patients with disc bulging and disc protrusion. In the disc protrusion group, the VAS scores in the first week after, the first month after and the sixth month after the procedure showed a significant decrease compared to the pre-procedure. There was no significant difference between the disc bulging and protrusion groups in the first week of post-procedure VAS score reduction. In the Disc Bulging group, the ODI score one week after, one month after, and six months after the procedure showed a significant decrease compared to the pre-procedure. In the Disc Protrusion group, the ODI score one week after, one month after, and six months after the procedure showed a significant decrease compared to the pre-procedure. Conclusion There was strong evidence that lumbar interlaminar steroid injection is an effective treatment for disc bulging and discogenic pain due to protrusion. When the ODI and VAS scores of patients with both disc bulging and disc protrusion were evaluated, it was seen that they benefited from epidural steroid injection. In the disc protrusion group, except for the first week of injection, relief due to the use of epidural steroids was observed to be greater compared to disc bulging.

Quenched Residual Stress Reduction in Pentagon-Curved Aluminum Alloy Forgings Using the Bulging Process

Quenched residual stress in pentagon-curved forgings (PCGs) often leads to severe deformation during subsequent machining operations. This study aims to mitigate the quenched residual stress in PCGs through the implementation of the bulging method. The edge distance ratio (e/D), a geometric characteristic of PCGs, is defined and considered in the established thermo-mechanical model, which incorporates the effects of quenched residual stress. Increasing e/D resulted in amplified maximum internal stresses and surface stresses. To address this issue, a bulging finite element (FE) model was developed to effectively alleviate the quenched residual stress. The stress reduction in surface stress and internal stress was qualified using average stress reduction (Ra) and peak stress reduction (Rp), respectively. Notably, stress reduction exhibited an inverse relationship with e/D, indicating that decreasing e/D yields greater stress reduction. Furthermore, an overall stress reduction assessment was conducted for different bulging ratios, revealing that the stress reduction increased as the bulging ratio increased. A comprehensive comparison of different bulging ratios highlighted 2% as the most optimal bulging ratio for stress reduction in PCGs. X-ray diffraction measurement and the contour method were employed to determine surface stress and internal stress, respectively. The experimental results were in agreement with the simulation outcomes, validating the high accuracy of the FE model.

Microsurgical phalloplasty: Anatomical study evaluating the use of the external pudendal vessels as recipients

The inferior epigastric artery (IEA) is commonly used as a recipient vessel in microsurgical phalloplasty but its use can be associated with abdominal parietal complications (hernia, bulging). To preclude such complications and avoid involvement of the femoral artery, we assessed an external pudendal artery (EPA) as a recipient vessel. We studied the disposition of the external pudendal system and its general anatomy. Then we compared the external diameter of the EPA to that of the first branches of the femoral artery. The most important point was to determine the location of the EPA through a reference line to facilitate a surgical approach. We then illustrated this preliminary study with a clinical case to check the reliability of the identified landmarks. Ten adult cadavers were dissected. The arteries of interest were part of a system consisting of either a common trunk or a duplicated system. The branches of the pudendal system arose from either the femoral artery or the deep femoral artery. On a horizontal reference line passing through the two pubic tubercles, we observed that 83% of EPAs arose between the reference line and 3 cm below it, at the level of a vertical axis centered on the femoral artery. The EPA could be suitable as recipient vessel in phalloplasty owing to its location, size, and ease of dissection. Using it instead of the IEA precludes abdominal parietal complications and reduces scarring in the recipient area.

Integration of Hot Tube Gas Forming and Die Quenching of Ultra-High Strength Steel Hollow Parts Using Low Pressure Sealed-Air

A low pressure sealed-air hot tube gas forming process of ultra-high strength steel tubes was developed not only to change the cross-section of the hollow products by bulging but also to increase the strength of components. Gas-formed components are typically formed by a controlled-gas pressure with extremely high internal pressure, which leads to affected production costs and safety. Moreover, compressing the gas with high pressure requires high energy during its preparation. Therefore, to simplify the internal pressure controlling system and improve the safety factor in gas forming processes, the sealed-air tubes are formed with a quite low initial pressure. The pressure of the sealed air increased with increasing temperature of the air inside the resistance-heated tube, and the bulging deformation was controlled only by axial feeding. The effects of the initial pressure and heating temperature on the bulging deformation and quenchability of the tubes, and the effect of the starting time of axial feeding on the bulging behavior were examined. Consequently, ultra-high strength steel bulged parts were produced even in low initial internal pressure and with the rapid heating of the tubes.

Flow-induced choking of a compliant Hele-Shaw cell

Harnessing flow–structure interactions has enabled the development of fluidic analogs of electronic circuit components, e.g., fluidic capacitors that store fluid much like an electrical capacitor stores charge. These soft components function in response to the flow; integrated into microfluidic devices, they remove the need for external actuation, thereby facilitating deployment outside of the laboratory. We describe a fluidic fuse that exploits the flow-induced deformation of a soft elastomer and identify the critical flow rate above which the flow is interrupted. This paves the way for the integration of passive flow limiters into microfluidic devices.

After centuries of striving for structural rigidity, engineers and scientists alike are increasingly looking to harness the deformation, buckling, and failure of soft materials for functionality. In fluidic devices, soft deformable components that respond to the flow have the advantage of being passive; they do not require external actuation. Harnessing flow-induced deformation for passive functionality provides a means of developing flow analogs of electronic circuit components such as fluidic diodes and capacitors. The electronic component that has so far been overlooked in the microfluidics literature—the fuse—is a passive safety device that relies on a controlled failure mechanism (melting) to protect a circuit from overcurrent. Here, we describe how a compliant Hele-Shaw cell behaves in a manner analogous to the electrical fuse; above a critical flux, the flow-induced deformation of the cell blocks the outflow, interrupting (choking) the flow. In particular, the pressure distribution within the fluid applies a spatially variant normal force to the soft boundary, which causes nonuniform deformation. As a consequence of lateral confinement and incompressibility of the soft material, this flow-induced elastic deformation manifests as bulging near the cell outflow; bulges that come into contact with the rigid cell roof interrupt the flow. We identify two nondimensional parameters that govern the central deflection and the choking of the cell, respectively. This study therefore provides the mechanical foundations for engineering passive-flow limiters into fluidic devices.

A Patient with a Large Basilar Artery Aneurysm in Whom Coil Embolization Was Performed by Protruding an LVIS into the Aneurysmal Neck in a Barrel-like Shape and Preserving a Branch Vessel

OBJECTIVE

We report a case of a low-profile visualized intraluminal support device (LVIS) being deployed and protruded into an aneurysmal neck in a barrel-like shape to perform dense coil embolization while preserving the branch vessel from the aneurysmal dome in order to prevent aneurysmal enlargement.

CASE PRESENTATION

A 74-year-old woman had a recurrent large cerebral aneurysm at the bifurcation of the basilar artery and the left superior cerebellar artery (SCA). Therefore, an LVIS was deployed from the left posterior cerebral artery to the basilar artery and protruded into the aneurysmal neck in a barrel-like shape to increase its metal coverage ratio. As the barrel-shaped protruding LVIS served as a scaffold to support the coils, dense coil embolization was performed while preserving the SCA branching from the aneurysmal dome. Images obtained at 6 months and 1 year after the embolization confirmed preservation of the SCA and prevention of aneurysmal enlargement.

CONCLUSION

Protruding the LVIS into an aneurysmal neck in a barrel-like shape is a technique that may help preserve the branch vessel and facilitate dense coil embolization.

Skeletal Muscle Shape Change in Relation to Varying Force Requirements Across Locomotor Conditions

Contractions of skeletal muscles to generate in vivo movement involve dynamic changes in contractile and elastic tissue strains that likely interact to influence the force and work of a muscle. However, studies of the in vivo dynamics of skeletal muscle and tendon strains remain largely limited to bipedal animals, and rarely cover the broad spectra of movement requirements met by muscles that operate as motors, struts, or brakes across the various gaits that animals commonly use and conditions they encounter. Using high-speed bi-planar fluoromicrometry, we analyze in vivo strains within the rat medial gastrocnemius (MG) across a range of gait and slope conditions. These conditions require changes in muscle force ranging from decline walk (low) to incline gallop (high). Measurements are made from implanted (0.5–0.8 mm) tantalum spheres marking MG mid-belly width, mid-belly thickness, as well as strains of distal fascicles, the muscle belly, and the Achilles tendon. During stance, as the muscle contracts, muscle force increases linearly with respect to gait–slope combinations, and both shortening and lengthening fiber strains increase from approximately 5 to 15% resting length. Contractile change in muscle thickness (thickness strain) decreases (r² = 0.86; p = 0.001); whereas, the change in muscle width (width strain) increases (r² = 0.88; p = 0.001) and tendon strain increases (r² = 0.77; p = 0.015). Our results demonstrate force-dependency of contractile and tendinous tissue strains with compensatory changes in shape for a key locomotor muscle in the hind limb of a small quadruped. These dynamic changes are linked to the ability of a muscle to tune its force and work output as requirements change with locomotor speed and environmental conditions.

Study on the Pressure Bearing Capability of Folded Multi-Port Flat Tube

The pressure bearing capability of a folded multi-port flat tube (MPFT), which has the advantage of retaining the corrosion property of corrosion resistant materials, was investigated in this study with both a burst pressure test and finite element simulation. Results show that the folded tube’s failure is mainly caused by the breaking of the inner ribs. Instead of detecting inner pressure, the bulging ratio, which is supposed to be small under service pressure, rises rapidly before failure. Therefore, it is suggested to use bulging ratio to visibly determine the working status of folded MPFTs. Based on FE simulations, the pressure bearing capability of the folded MPFT was improved by optimizing the relevant folding parameters. In addition, the influence of in-plane bending was also investigated. It is found that the folded MPFTs can still retain most of the pressure bearing capability after in-plane bending.

Quantitative analysis of indirect decompression in extreme lateral interbody fusion and posterior spinal fusion with a percutaneous pedicle screw system for lumbar spinal stenosis

BACKGROUND

The authors sought to quantify the results of clinical and radiological analyses of extreme lateral interbody fusion (XLIF) plus percutaneous pedicle screw (PPS) fixation for patients with lumbar spinal stenosis (LSS) by focusing on the distinct mechanism of indirect decompression.

METHODS

Data obtained from a total of 37 patients with 47 surgical sites were retrospectively analyzed. Clinical outcomes for all patients were evaluated using the Japanese Orthopaedic Association (JOA) score and the improvement rate of the JOA score. Preoperative and postoperative magnetic resonance images were used to measure the transverse areas of both the dural sac (DS area) and ligamentous flavum (LF area) in the axial sections and the length of the intervertebral disc bulge (DB length) in sagittal sections. Then, the rate of change (RC) of the DS area (RC-DS), the RC of the LF area (RC-LF), and the RC of the DB length (RC-DB) from the preoperative period to the postoperative period were calculated. Furthermore, we divided all surgical sites into the small expansion group (SE group; RC-DS <150%) and large expansion group (LE group; RC-DS ≥200%) according to the degree of RC-DS.

RESULTS

Preoperative clinical symptoms improved significantly after surgery for all patients regardless of whether the RC-DS was large or small. RC-DS, RC-LF, and RC-DB were approximately 203%, 74%, and 37%, respectively. Moreover, we found that the bulging was significantly shorter in the LE group than in the SE group, although there was no difference in the RC-LF between the LE group and SE group.

CONCLUSIONS

We suggest that indirect decompression after XLIF is particularly influenced by the degree of reduction in DB.

Surface Roughening Behavior of 6063 Aluminum Alloy during Bulging by Spun Tubes

Severe surface roughening during the hydroforming of aluminum alloy parts can produce surface defects that severely restrict their application in the automobile and aerospace industry. To understand the relation between strain, grain size and surface roughness under biaxial stress conditions, hydro-bulging tests of aluminum alloy tubes were carried out, and the tubes with different grain sizes were prepared by a spinning and annealing process. The surface roughness was measured by a laser scanning confocal microscope to evaluate the surface roughening macroscopical behavior, and the corresponding microstructures were observed using electron back-scattered diffraction (EBSD) to reveal the roughening microscopic behavior. The results obtained show that the surface roughness increased with both strain and grain size under biaxial stress. No surface defects were observed on the surface when the grain size was less than 105 μm if the strain was less than 18%, or when the grain size was between 130 and 175 μm if the strain was less than 15.88% and 7.15%, respectively. The surface roughening microscopic behavior was identified as an inhomogeneous grain size distribution, which became more pronounced with increasing grain size and resulted in greater local deformation. Concentrated grain orientation also results in severe inhomogeneous deformation during plastics deformation, and serious surface roughening.

Estimation of solid-liquid interfacial tension using curved surface of a soft solid

Unlike liquids, for crystalline solids the surface tension is known to be different from the surface energy. However, the same cannot be said conclusively for amorphous materials like soft cross-linked elastomers. To resolve this issue we have introduced here a direct method for measuring solid-liquid interfacial tension by using the curved surface of a solid. In essence, we have used the inner surface of tiny cylindrical channels embedded inside a soft elastomeric film for sensing the effect of the interfacial tension. When a liquid is inserted into the channel, because of wetting-induced alteration in interfacial tension, its thin wall deflects considerably; the deflection is measured with an optical profilometer and analyzed using the Föppl-von Kármán equation. We have used several liquids and cross-linked poly(dimethylsiloxane) as the solid to show that the estimated values of the solid-liquid interfacial tension matches with the corresponding solid-liquid interfacial energy reasonably well.

Knockin' on pollen's door: live cell imaging of early polarization events in germinating Arabidopsis pollen

Pollen tubes are an excellent system for studying the cellular dynamics and complex signaling pathways that coordinate polarized tip growth. Although several signaling mechanisms acting in the tip-growing pollen tube have been described, our knowledge on the subcellular and molecular events during pollen germination and growth site selection at the pollen plasma membrane is rather scarce. To simultaneously track germinating pollen from up to 12 genetically different plants we developed an inexpensive and easy mounting technique, suitable for every standard microscope setup. We performed high magnification live-cell imaging during Arabidopsis pollen activation, germination, and the establishment of pollen tube tip growth by using fluorescent marker lines labeling either the pollen cytoplasm, vesicles, the actin cytoskeleton or the sperm cell nuclei and membranes. Our studies revealed distinctive vesicle and F-actin polarization during pollen activation and characteristic growth kinetics during pollen germination and pollen tube formation. Initially, the germinating Arabidopsis pollen tube grows slowly and forms a uniform roundish bulge, followed by a transition phase with vesicles heavily accumulating at the growth site before switching to rapid tip growth. Furthermore, we found the two sperm cells to be transported into the pollen tube after the phase of rapid tip growth has been initiated. The method presented here is suitable to quantitatively study subcellular events during Arabidopsis pollen germination and growth, and for the detailed analysis of pollen mutants with respect to pollen polarization, bulging, or growth site selection at the pollen plasma membrane.