Dumbbell Shape Research Articles

Sintering Behavior of Bi-Material Micro-Component of 17-4PH Stainless Steel and Yttria-Stabilized Zirconia Produced by Two-Component Micro-Powder Injection Molding Process.

In this research, we investigated the influence of the sintering temperature on the physical and mechanical properties of micro-sized bi-material components of 17-4PH stainless steel and 3 mol% yttria-stabilized zirconia fabricated using a two-component micro-powder injection molding (2C-μPIM) process. First, 17-4PH and zirconia powders were separately mixed with binders to obtain feedstocks, which were then injection-molded into the dumbbell shape, followed by the binder extraction process. Subsequently, the debound micro-specimens were subjected to sintering between 1250 °C and 1350 °C for 3 h. Per the observations of the microstructures using scanning electron microscopy (SEM), a strong bond between metal and ceramic in micro-sized 17-4PH/zirconia components was formed when the sintering temperature exceeded 1300 °C. The maximum relative density of 99% was achieved when the bi-material micro-part was sintered at 1350 °C. The linear shrinkage increased from 9.6% to 17.4% when the sintering temperature was increased from 1250 °C to 1350 °C. The highest hardness value of 1439.6 HV was achieved at 1350 °C along the bi-material bonding region. Moreover, a maximum tensile strength of 13.7 MPa was obtained at 1350 °C.

Clinical Features and Outcomes of Patients with Orbital Schwannoma.

To report the clinical features, treatment, and outcome of 11 patients with orbital schwannoma in Korean patients. The medical records of 11 orbital schwannoma patients treated between April 2007 and April 2021 were retrospectively reviewed. The demographic data, clinical characteristics, radiological features, and outcomes were reviewed. The mean age at the time of diagnosis was 49.00 ± 14.45 years. The most common initial symptom was ocular protrusion (n = 7), and other symptoms were decreased visual acuity ( n = 5), restriction of eye movement ( n = 4), swelling ( n = 3), and pain ( n = 2). Locations of tumors were superomedial; followed by the orbital apex and inferolateral. The most common shape seen in our patients was beads like multilobulated appearance; followed by a round, oval, fusiform, and dumbbell shape. MRI of T1-weighted revealed isointense or hypointense, whereas the T2-weighted indicated hyper or isointense lesion. Five patients had optic neuropathy at presentation, and 1 of them showed improved vision after surgery. Complete or incomplete excision was performed for all. Surgical complications include decreased vision and paraesthesia. There has been no recurrence to date. Orbital schwannoma is a rare disease and it is difficult to distinguish it from other orbital tumors because the initial symptoms are nonspecific. Differential diagnosis by combining the shape, location, and contrast enhancement findings seen on computed tomography and magnetic resonance imaging can be helpful in surgical treatment. Complete excision gives the best results without recurrence, but if the patient is in an inaccessible location, only surgery to reduce the volume can satisfy the patient without recurrence.

Chemically Stable Low-Dimensional Electrides in Transition Metal-Rich Monochalcogenides: Theoretical and Experimental Explorations

Electrides, which are ionic crystals composed of excess anionic electrons, are of great interest as an exotic material for fundamental research and practical applications in broad fields of science and technology. However, an inherent chemical instability under ambient conditions at room temperature has been a fatal drawback to be addressed. Here, we report that transition metal-rich monochalcogenides are an emerging class of low-dimensional electrides with excellent chemical and thermal stability in air and water at room temperature through a comprehensive exploration of theoretical prediction and experimental verification. We predict new two-dimensional (2D) electrides crystallized in hexagonal P3̅m1 and P63/mmc structures with strong localization of anionic electrons in a dumbbell shape at the tetrahedral cavity of the interlayer space, which are distinct from the anionic electrons localized at the octahedral cavity in the hexagonal R3̅m structure of the previous 2D [Ca2N]+·e- and [Y2C]2+·2e- electrides. We successfully synthesized the room-temperature stable [Ti2O]2+·2e-, [Ti2S]2+·2e-, [Zr2S]2+·2e-, and primary solid solution [Hf2SxSe1-x]2+·2e- electrides, showing no structural degradation in air and water. Among them, we found that the synthesized [Ti2S]2+·2e- and [Zr2S]2+·2e- electrides are crystallized in orthorhombic symmetry (Pnnm), showing the feature of a one-dimensional (1D) electride with an anionic electron chain, which has never been reported yet. In addition to the successful finding of new 1D and 2D electrides, we discuss the self-passivation effect-driven chemical stability and the role of anionic electrons in determining the physical properties of the newly discovered electrides.

Feasibility experiments of seismic concrete block walls without joint mortar

The authors developed two types of block systems consisting only of main block and key block without joint mortar in consideration of seismic performance and workability. Two types of block systems have different key block shapes: One is the peanuts shape and the other is the dumbbell shape. In this study, the proposed two types of block walls as well as a typical block wall were experimentally investigated to evaluate the seismic performance. In the tests, full-scale, single-story specimens were tested under static cyclic in-plane loading, and failure patterns and cracks were carefully observed. In this paper, the loading bearing capacity, energy dissipation capacity and reuse ratio of block walls are discussed in detail. As a result, the deformability, energy absorption capacity and reuse ratio of the proposed block systems were considerably higher than those of typical block system.

Improvement in Strain Sensor Stability by Adapting the Metal Contact Layer.

Research on stretchable strain sensors is actively conducted due to increasing interest in wearable devices. However, typical studies have focused on improving the elasticity of the electrode. Therefore, methods of directly connecting wire or attaching conductive tape to materials to detect deformation have been used to evaluate the performance of strain sensors. Polyaniline (PANI), a p-type semiconductive polymer, has been widely used for stretchable electrodes. However, conventional procedures have limitations in determining an appropriate metal for ohmic contact with PANI. Materials that are generally used for connection with PANI form an undesirable metal-semiconductor junction and have significant contact resistance. Hence, they degrade sensor performance. This study secured ohmic contact by adapting Au thin film as the metal contact layer (the MCL), with lower contact resistance and a larger work function than PANI. Additionally, we presented a buffer layer using hard polydimethylsiloxane (PDMS) and structured it into a dumbbell shape to protect the metal from deformation. As a result, we enhanced steadiness and repeatability up to 50% strain by comparing the gauge factors and the relative resistance changes. Consequently, adapting structural methods (the MCL and the dumbbell shape) to a device can result in strain sensors with promising stability, as well as high stretchability.

Piezo-resistive effects of Area-arrayed Dumbbell-Shape Graphene Nano-ribbon Structure for Highly Sensitive Micro-Scale Tactile Sensor

In order to develop a highly-sensitive small-scale tactile sensor, piezoresistive effect of graphene nanoribbon was applied to the sensor. It was confirmed that the graphene nanoribbon narrower than about 70 nm showed semiconductive properties and thus, large piezo-resistive constant. The dumbbell shape was applied to the stable junction between metallic graphene and semiconductive graphene. It was easy to form stable ohmic contact between the metallic graphene and metallic electrode. An area-arrayed nanoscale GNR structure with varying width was fabricated for a highly sensitive tactile sensor. Graphene was synthesized inside a copper pocket using a low-pressure chemical vapour deposition (LP-CVD) method. PMMA- assisted wet transfer process was used to transfer graphene grown on the copper to the target substrate. Then, the electrodes were deposited using electron-beam deposition. A four-point bending test was carried out on the sensor to determine the piezo-resistive effect of the DS-GNR. Finally, the gauge factor was determined under the application of various amounts of strain.

Tensile properties of epoxy resin filled with activated carbon derived from coconut shell

Epoxy is one of the most widely used polymers. The aim of this research is to determine the potential of activated carbon derived from coconut shells as fillers in epoxy resin. 5 wt% of this filler was added to epoxy resin. The entire specimens were manufactured using a mold made out of aluminum strips with dumbbell shape according to ASTM D638 standard. Tensile properties of epoxy resin with and without filler were analyzed to observe the effect of activated carbon. The results showed that the addition of 5 wt% of activated carbon can decrease the tensile strength of epoxy resin, meanwhile increasing its elastic modulus.

Rapid photodegradation of linezolid antibiotic and methylene blue dye over Pt nanoparticles/polypyrrole-carbon black/ZnO novel visible light photocatalyst

Exhaustive efforts are urgently anticipated in photocatalysis to tackle the present grave environmental problems especially water pollution. The proposed work aims to provide decidedly active visible light inclined ternary photocatalyst consists of ZnO nanostructure having admirable photocatalytic activity merely doped with polypyrrole-carbon black (PPy-C) and Pt nanoparticles for environmental concerns. Pt and PPy-C doped ZnO ternary framework was created via a reformed sol-gel route and a facile ultrasonication methodology. The XRD examination revealed that ZnO possesses a hexagonal wurtzite structure, while FTIR and XPS investigations established the efficacious formation of ternary framework among Pt, PPy-C and ZnO nanostructures. The TEM exploration displayed that Pt nanoparticles (3–8 nm) were successfully disseminated on ZnO nanostructures (~20–120 nm) associated with spongy dumbbell shape PPy-C, recommending the ternary photocatalyst development. The UV–vis spectroscopic analysis showed a lowering in band-gap energies upon Pt and PPy-C incorporation. This newly synthesized Pt@PPy-C/ZnO photocatalyst has been successfully employed to photo-catalytically treat linezolid (an antibiotic drug) and methylene blue (MB) dye using visible-light. This Pt@PPy-C/ZnO photocatalyst showed amazing activity with 94.0% elimination of linezolid drug in just 40 min with ultrafast removal rate that is approximately 1.67 fold than undoped ZnO. Moreover, this Pt@PPy-C/ZnO ternary framework has proven to be very influential in removing MB using visible light irradiation.

Normal & reversed spin mobility in a diradical by electron-vibration coupling

π−conjugated radicals have great promise for use in organic spintronics, however, the mechanisms of spin relaxation and mobility related to radical structural flexibility remain unexplored. Here, we describe a dumbbell shape azobenzene diradical and correlate its solid-state flexibility with spin relaxation and mobility. We employ a combination of X-ray diffraction and Raman spectroscopy to determine the molecular changes with temperature. Heating leads to: i) a modulation of the spin distribution; and ii) a “normal” quinoidal → aromatic transformation at low temperatures driven by the intramolecular rotational vibrations of the azobenzene core and a “reversed” aromatic → quinoidal change at high temperatures activated by an azobenzene bicycle pedal motion amplified by anisotropic intermolecular interactions. Thermal excitation of these vibrational states modulates the diradical electronic and spin structures featuring vibronic coupling mechanisms that might be relevant for future design of high spin organic molecules with tunable magnetic properties for solid state spintronics.

Myoepithelioma in the parapharyngeal space report of two cases and review of literature

<br><b>Introduction:</b> Myoepithelioma (ME) is a benign tumour in 40% of cases located in the parotid gland, accounting for <11.5% of all salivary gland tumours. Myoepitheliomas arise from myoepithelial cells, which are present in major and minor salivary glands, but also lacrimal glands, breasts, and sweat glands. They are seen more often between the fourth and fifth decade of life, without sex predominance. Patients mainly complain about painless, slowly growing mass. MEs in CT are characterized as well-circumscribed small, unilocular, round tumours with smooth or lobulated contours; they may contain enhancing nodules and non-enhancing areas and exhibit homogeneous signal intensities or densities based on MRI. Deep lobe parotid tumours may occasionally grow along the stylomandibular tunnel into the parapharyngeal region resembling dumbbell shape. Tumours of the parapharyngeal space are rare and account for 0.50.8% of all head and neck tumours. Patients have an intraoral mass or asymmetry of the palate, with difficulties in swallowing or phonation. Operative removal with capsule preservation is the treatment of choice. The approach depends on the size of the tumour: cervical, transoral, transparotid, mandibular osteotomy approach or a combination of these. MEs may be locally aggressive, especially in long-standing tumours or in tumours with multiple recurrences.</br> <br><b>Case report:</b> The authors present two cases of myoepithelioma in the parapharyngeal space.</br>

Acrylonitrile-Styrene-Acrylate Particles with Different Microstructure for Improving the Toughness of Poly(styrene-co-acrylonitrile) Resin

Herein, acrylonitrile-styrene-acrylate copolymer (ASA) particles with different microstructure were synthesized by emulsion polymerization and then used for toughening poly(styrene-co-acrylonitrile) (SAN) resin. The structure of ASA particles was confirmed by FTIR. TEM results demonstrated that the particles with different morphologies of multilobe shape, complete core-shell and dumbbell shape were obtained depending on the cross-linker amount. It was found that the toughening efficiency reached the highest when the ASA particles had complete core-shell structure and the shell composition was close to that of the SAN matrix. It was ascribed to the fact that the complete shell layer and similar shell composition provided sufficient interfacial adhesion and transferred stress to induce larger matrix deformation, so that the notched impact strength increased accordingly. Moreover, the notched impact strength of SAN/ASA blend was improved without significantly sacrificing tensile strength when adding 30 wt% ASA particles with the size of around 400 nm. SEM results of the impact-fractured surfaces revealed that irregular fluctuation and numerous microvoids occurred. It was deduced that the toughening mechanism was attributed to the crazings and cavitation of particles. Therefore, this study paved a way of toughening the resin by adjusting the microstructure of the particles including morphology, composition, and size.

(216) Kleopatra, a low density critically rotating M-type asteroid

Context. The recent estimates of the 3D shape of the M/Xe-type triple asteroid system (216) Kleopatra indicated a density of ~5 g cm−3, which is by far the highest for a small Solar System body. Such a high density implies a high metal content as well as a low porosity which is not easy to reconcile with its peculiar “dumbbell” shape. Aims. Given the unprecedented angular resolution of the VLT/SPHERE/ZIMPOL camera, here, we aim to constrain the mass (via the characterization of the orbits of the moons) and the shape of (216) Kleopatra with high accuracy, hence its density. Methods. We combined our new VLT/SPHERE observations of (216) Kleopatra recorded during two apparitions in 2017 and 2018 with archival data from the W. M. Keck Observatory, as well as lightcurve, occultation, and delay-Doppler images, to derive a model of its 3D shape using two different algorithms (ADAM, MPCD). Furthermore, an N-body dynamical model allowed us to retrieve the orbital elements of the two moons as explained in the accompanying paper. Results. The shape of (216) Kleopatra is very close to an equilibrium dumbbell figure with two lobes and a thick neck. Its volume equivalent diameter (118.75 ± 1.40) km and mass (2.97 ± 0.32) × 1018 kg (i.e., 56% lower than previously reported) imply a bulk density of (3.38 ± 0.50) g cm−3. Such a low density for a supposedly metal-rich body indicates a substantial porosity within the primary. This porous structure along with its near equilibrium shape is compatible with a formation scenario including a giant impact followed by reaccumulation. (216) Kleopatra’s current rotation period and dumbbell shape imply that it is in a critically rotating state. The low effective gravity along the equator of the body, together with the equatorial orbits of the moons and possibly rubble-pile structure, opens the possibility that the moons formed via mass shedding. Conclusions. (216) Kleopatra is a puzzling multiple system due to the unique characteristics of the primary. This system certainly deserves particular attention in the future, with the Extremely Large Telescopes and possibly a dedicated space mission, to decipher its entire formation history.

Motion of generated dumbbell-shaped satellite droplets during liquid dielectrophoresis

Actuation of sub-millimeter sized droplets has important implications in heat transfer, microfluidics, and self-cleaning surfaces. Here, we report the motion of satellite droplets generated around a primary droplet actuated using liquid dielectrophoresis (L-DEP). Satellite droplets spanning the electrode gap grow due to the electric field induced enhanced merging of droplets. These satellite droplets attain a dumbbell shape due to the applied field. Interestingly, satellite droplets follow the primary drop interface maintaining a constant gap between themselves and the primary drop. The motion of satellite droplets was captured using high-speed imaging, and the role of temperature gradient was verified by measuring temperature distribution using an IR camera. Through observations and simulations, we qualitatively believe that this behavior arises from (a) repulsive electrostatic and temperature gradient forces; and (b) attractive vapor concentration gradient forces. Simulations were used to estimate the direction of individual forces. Interfacial charges from the applied electric field give rise to the electrostatic repulsion. During L-DEP, the primary droplet heats due to induced current. Thermal conduction through the substrate sets up a temperate gradient, which adds to the repulsion forces between the droplets. Evaporation of the primary droplet leads to the vapor concentration gradient, responsible for the attraction force between the droplets.

The magnetic resonance enterography imaging features of symptomatic Meckel's diverticulum in pediatric patients: a retrospective observational study of 31 cases.

BackgroundThe aim of this study was to explore the magnetic resonance enterography (MRE) imaging manifestations of a symptomatic Meckel’s diverticulum (MD) in pediatric patients in order to provide a reference for the diagnosis of the condition.MethodsThe medical records of 31 pediatric patients with MD from May 2014 to October 2020 were retrospectively analyzed. The inclusion criteria were patients with MD accompanied by unexplained gastrointestinal bleeding, anemia (except hematological diseases), chronic persistent abdominal pain, repeated intussusception, or intussusception in older pediatric patients during surgery. The clinical variables (age, sex, and hemoglobin) and imaging, surgical, and pathological findings were recorded.ResultsMD was definitively identified in 28 patients, with the following characteristics: a blind-ending fluid-filled and/or gas-filled structure (n=23), an elongated shape (n=1), a dumbbell shape (n=1), and a solid mass (n=3). The diverticula were located in the right lower quadrant (n=16), the right abdomen at the level of the umbilicus (n=3), the right upper quadrant (n=2), the left upper quadrant (n=2), and the midline lower abdomen (n=5). Supply arteries were visualized in nine cases. In all cases, mural enhancement was comparable to that of the adjacent small-bowel (SB). Extravasation of the intravascular contrast medium was seen in two cases. Peripheral structural abnormalities included mesenteric fat stranding (n=7), hemorrhage in the adjacent lumen (n=3), free intraperitoneal gas (n=1), abnormal fluid retention (n=2), intestinal obstruction (n=1), and lymph node enlargement (n=7). A normal appendix was identified in 18 cases.ConclusionsMRE is an appropriate method of diagnosing symptomatic MD in pediatric patients and is particularly useful in the assessment of complications.

Aesthetic Nasal Lobule Correction Using a Three-Dimensional Printed Polycaprolactone Implant.

Nasal tip plasty is a surgery that determines important rhinoplasty outcomes. A variety of autologous and alloplastic implants are utilized in this procedure, including 1 synthetic material known as polycaprolactone (PCL). This study provides background on the ready-made three-dimensional printed PCL implant for nasal lobule correction, before discussing the usefulness and effectiveness of the implant. A total of 23 patients who visited our hospital between January 2018 and January 2020 were evaluated in this study. We used 3 types of PCL implant to get an ideal shape for the nasal tip: tipball (globular shape), droneball (rugby ball shape), and dumbbell (dumbbell shape). The authors compared nasolabial angle and tip projection at the preoperative and postoperative period via photographic anthropometric analysis. In 4 patients, we also examined the dead space between the implant and soft tissue via ultrasonography. The follow-up period averaged 9.5 months and no serious complications were found after surgery. The nasolabial angle and tip projection had an average postoperative increase of 6.4° and 0.044, respectively. Ultrasonography revealed the attachment of the implant at the insertion site and no dead space was found. This is the first attempt to apply a ready-made three-dimensional printed PCL implant to a nasal lobule correction procedure. As the implant was easy to use and showed good results, it may be useful for aesthetic purposes in future nasal tip plasty procedures.

Control Over the Morphology of Electrospun Microfibrous Mats of a Polymer of Intrinsic Microporosity.

This study reports for the first time the preparation of an electrospun microfibrous mat of PIM-EA-TB. The electrospinning was carried out using a chloroform/n-Propyl-lactate (n-PL) binary solvent system with different chloroform/nPL ratios, in order to control the morphology of the microfibres. With pure chloroform, porous and dumbbell shape fibres were obtained whereas, with the addition on n-PL, circular and thinner fibres have been produced due to the higher boiling point and the higher conductivity of n-PL. The electrospinning process conditions were investigated to evaluate their impact on the fibres’ morphology. These microfibrous mats presented potential to be used as breathable/waterproof materials, with a pore diameter of 11 μm, an air resistance of 25.10−7 m−1 and water breakthrough pressure of 50 mBar.

Percutaneous major aortopulmonary collateral artery banding using a covered stent in an infant.

We report a 6-month-old infant with pulmonary atresia with ventricular septal defect who was successfully treated with a novel technique of percutaneous major aortopulmonary collateral artery (MAPCA) banding with a covered stent. He suffered from heart failure due to a residual MAPCA of 4.5 mm in diameter. A covered stent tied with 2 5-0 size nylon threads was successfully deployed into the MAPCA in a dumbbell shape with a banding diameter of 2.8 mm. Banding covered stent implantation is a useful method to reduce the pulmonary blood flow in patients with MAPCA, which could be a less-invasive alternative to surgery.

Nanoparticles: Untying the Gordian Knot in Conventional Computed Tomography Imaging

X-ray computed tomography (CT) imaging plays an essential role in disease diagnosis due to its noninvasive, painless mode and superior penetration depth. However, the resolution of the soft tissue ...

Investigation of morphologically tuned Sb2S3 nanostructures as an effective electrocatalyst for hydrogen evolution reaction

A simple solvothermal route has been adopted for the successful development of morphologically varied Sb2S3 nanostructures by incorporating various organic complex reagents into the reaction process. The prepared Sb2S3 nanostructures were investigated for electrocatalytic performance towards HER. The nanostructured Sb2S3 (PVP) catalyst exhibiting dumbbell shape formed together by the aggregation of nanowires revealed better performance in catalyzing HER with low overpotential of − 0.168 V vs. RHE in attaining the current density of 10 mA/cm2 when compared with other catalyst possessing different morphology. It also revealed least Tafel slope value of 85 mV/dec corroborating that the reaction kinetics follows Volmer-Heyrovsky step. The nanowires possess large number of active surface sites and interfaces as it facilitates transfer of charges across the electrode-electrolyte interface which helped in the evolution of hydrogen molecules more rapidly with low onset potential.

Commentary: Anterior Petrosal Approach for Enlarging Previously Radiated Recurrent Trigeminal Schwannoma: 2-Dimensional Operative Video.

Trigeminal nerve schwannomas (TNSs) are rare lesions that typically present with symptoms of trigeminal neuropathy or other cranial nerve palsies. These lesions classically have a dumbbell shape, with an anterior component within Meckel's cave and posterior component extending into the posterior fossa through the porus trigeminus. Surgical resection of TNSs can often be achieved via an extradural subtemporal approach to Meckel's cave without an anterior petrousectomy, even for tumors with a significant posterior fossa component, as the tumor often erodes a portion of the petrous apex.1 We present the case of a 53-yr-old female presenting to our institution with complete trigeminal neuropathy secondary to a right-sided, previously resected and radiated TNS. Serial imaging demonstrated an interval growth of significant residual tumor despite multiple adjuvant therapies, and, thus, the patient was recommended to undergo additional surgical resection. The lesion was approached through a right-sided subtemporal approach to Meckel's cave,2 with a plan to utilize an anterior petrousectomy only if difficulty resecting the posterior fossa component of the tumor was encountered. Intraoperatively, the posterior fossa component was found to be densely adherent to the adjacent brainstem, likely secondary to prior surgery and radiation therapy, and, thus, an anterior petrousectomy was performed. Postoperatively, the patient had stable trigeminal neuropathy without any new neurological deficits and a magnetic resonance imaging (MRI) confirmed a gross total resection. In the accompanying video, we hope to demonstrate the steps and nuances of both the subtemporal approach to accessing Meckel's cave and anterior petrousectomy when employed for the resection of TNSs. The patient in question provided formal consent for the making of this video.