Dumbbell Type Research Articles

Study on collapse controlling of single-wall carbon nanotubes by helium storage

In this paper, we propose a method to control the collapsed nanostructurings of single-walled carbon nanotubes (SWCNTs) by helium storage and the key mechanism is elaborated from the potential energy aspect. The molecular dynamics simulation shows that enough helium atoms could restore the collapsing configuration of (40, 40) carbon nanotubes back to the circular cross section. The length of the flat double carbon atoms layer in the dumbbell type structure and the diameter of nearly circular edges can be precisely altered by adjusting the helium atom numbers. Two key storage rates are introduced to classify the final nanostructures of (5n, 5n) SWCNTs. The relationship between helium numbers and the final configuration is investigated; the analysis method that introduces helium atoms into the cavity of SWCNTs can also be extended to other kinds of molecules.

Microfluidic Fabrication of Morphology-Controlled Polymeric Microspheres of Blends of Poly(4-butyltriphenylamine) and Poly(methyl methacrylate).

Multicomponent polymer particles with specific morphology are promising materials exhibiting novel functionality which cannot be obtained with single-component polymer particles. Particularly, the preparation of such kinds of polymer particles involving electrically or optically active conjugated polymers with uniform size is a challenging subject due to their intense demands. Here, microspheres of binary polymer blend consisting of poly(4-butyltriphenylamine) (PBTPA)/poly(methyl methacrylate) (PMMA) (1:1 in weight) were produced via a microfluidic emulsification with a Y-shaped microreactor, and a subsequent solvent evaporation method. The flow rate of the dispersed phase (polymer solution) was fixed to 7 µL/min, and 140 or 700 µL/min of the flow rate of the continuous phase (aqueous 0.6 wt % of poly(vinyl alcohol) (PVA) solution) was utilized to produce the dispersion with different diameter. The concentration of dispersed phase was adjusted to 0.1 or 1.0 w/v%. Core-shell, Janus and dumbbell type microspheres were obtained dependent on the flow rate of continuous phase. Incomplete core-shell type microspheres were produced for the blend involving low molecular weight PMMA. Complex Janus and core-shell type microspheres were fabricated by the addition of sodium dodecyl sulfate (SDS) to continuous phase. It is found that final morphologies are strongly dependent on the initial conditions of dispersion including the particle size suggesting that the morphologies are governed by the kinetical factors together with the conventionally accepted thermodynamic ones.

Surgical Technique for Lumbar Spinal Extraforaminal Schwannoma

Spinal neurinomas are frequently observed in the cauda equina, particularly within the dura mater. However, extraforaminal schwannomas(EFS), which are neither intradural nor dumbbell type, are relatively rare; hence, different surgical procedures have been employed. Here, we report 12 cases of lumbar EFS with total resection that were safely performed. This study was comprised of 12 patients with lumbar EFS(excluding those with neurofibromas)who were previously treated at our hospital. Using the Wiltse paraspinal approach, we inserted the microscope until it reached the tumor surface. After confirming the tumor surface, we inserted a scalpel to make an incision in a portion of the outer capsule. Then, we confirmed that the surfaces of the outer capsule and the tumor within the capsule could be dissected. Next, a thread was attached to the outer capsule and pulled upwards so that there was enough space to perform the required procedures within the capsule. Using a CUSA^®, we removed the intracapsular tumor. After its removal, the outer capsule was treated carefully to ensure that the origin nerve was not damaged. In all cases, we successfully performed a total removal of the intracapsular tumor;in the mean postoperative observation period of 8 years, no recurrence was observed. Although temporary paralysis was observed in three patients, this improved over time. We report our experience with a surgical technique that ensured the safe removal of lumbar EFS. Satisfactory results were achieved, with no recurrences observed during the mean 8-year postoperative observation period.

Effect of Lignin and CNTs on the properties of melt-spun polymeric fibers

The quality of high density polyethylene (HDPE) - lignin spun fibers depends on the spinning method and the chemical modification of the raw material. On the other hand, nylon-type polymers are widely known for their simple experimental synthesis and use. The goal of this study was the fabrication of composites containing lignin, nylon and multi-walled carbon nanotubes (MWCNTs) based fibers with enhanced mechanical properties. Therefore, a nylon-type polymer was synthesized, using diethylenetriamine and sebacoyl chloride, and was conjugated with lignin as well as MWCNTs with the aim of determining the materials' compatibility, differences in chemical behavior as well as their ability to be melt spun and be further processed. The materials were compounded with HDPE and melt spun, producing fibers that were characterized in respect of their morphology, structural, chemical and elemental composition. Finally, the HDPE fibers were used for the production of one dimensional composites inside dumb bell type sacrificial templates with an epoxy resin solution. The composites, which contained fibers enriched with oxidized lignin and MWCNTs, presented higher elastic modulus and ultimate tensile strength than the rest of the composites. This is a novel attempt, presenting an innovation concerning durable fibers with low cost materials and procedures.

Computational Model and Dynamics of Monomeric Full-Length APOBEC3G.

APOBEC3G (A3G) is a restriction factor that provides innate immunity against HIV-1 in the absence of viral infectivity factor (Vif) protein. However, structural information about A3G, which can aid in unraveling the mechanisms that govern its interactions and define its antiviral activity, remains unknown. Here, we built a computer model of a full-length A3G using docking approaches and molecular dynamics simulations, based on the available X-ray and NMR structural data for the two protein domains. The model revealed a large-scale dynamics of the A3G monomer, as the two A3G domains can assume compact forms or extended dumbbell type forms with domains visibly separated from each other. To validate the A3G model, we performed time-lapse high-speed atomic force microscopy (HS-AFM) experiments enabling us to get images of a fully hydrated A3G and to directly visualize its dynamics. HS-AFM confirmed that A3G exists in two forms, a globular form (∼84% of the time) and a dumbbell form (∼16% of the time), and can dynamically switch from one form to the other. The obtained HS-AFM results are in line with the computer modeling, which demonstrates a similar distribution between two forms. Furthermore, our simulations capture the complete process of A3G switching from the DNA-bound state to the closed state. The revealed dynamic nature of monomeric A3G could aid in target recognition including scanning for cytosine locations along the DNA strand and in interactions with viral RNA during packaging into HIV-1 particles.

Solitary Osteochondroma Presenting as a Dumbbell Tumor Compressing the Cervical Spinal Cord.

We report a case of a solitary osteochondroma as a dumbbell tumor compressing the spinal cord and its surgical strategy. The patient is a 16-year-old female with longstanding posterior neck pain and left arm abduction weakness. She was examined by plain X-ray, three-dimensional-computed tomography, magnetic resonance imaging, and vertebral angiography. The analyses indicated a calcified extradural mass compressing the cord in the C3–4 portion extending into the neural and vertebral foramen with eroded vertebral body. The tumor was successfully excised using a modified combined anterior and posterior approach. Histopathologic study of the resected material confirmed the diagnosis. The postoperative assessment was followed by clinical and radiologically therapy for 5 years after surgery. Osteochondroma arises from enchondral bone but it rarely involves the spine, especially not as s dumbbell type. In this patient, the tumor may have arisen from the neural arch and extended into the extradural and extraforaminal space over a long period. We successfully removed the dumbbell tumor with a combined anterior oblique and posterior approach. However, further observation is essential because of the possibility of recurrence and sarcomatous change.

Electrochemical surface functionalization of carbon fibers for chemical affinity improvement with epoxy resins

The purpose of this study is to increase the wetting properties of carbon fibers in order to improve the adhesion force between the fiber and the polymer matrix. Commercial carbon fibers were surface functionalized through cyclic voltammetry together with potentiostatic conditions in aqueous electrolyte solutions of H2SO4, in the presence of acrylic acid, methacrylic acid, acrylonitrile and N-vinylpyrrolidone monomers. The anodic and cathodic peaks were correlated with oxide formation and their partial reduction, respectively. The produced surface modified carbon fibers were wetted with epoxy resin so that to produce dumbbell type composites for tensile strength testing. The nature of oxygen containing groups on the fibers surface was determined by Fourier-transform infrared and Raman spectroscopy. Moreover, the wetting properties of the treated carbon fibers were evaluated via contact angle measurements whereas the morphology of the coated fibers was investigated via scanning electron microscopy. Finally, the mechanical performance of the composites was evaluated by means of tensile testing and strength measurements.

Contrast MRI Findings for Spinal Schwannoma as Predictors of Tumor Proliferation and Motor Status.

Retrospective analysis. The goal of this study was to examine the relationship of the proliferation potency based on the MIB-1 index and motor status with features of T2-weighted images (T2WI) and contrast T1-weighted images (T1WI) of spinal schwannoma. Spinal schwannomas account for 55% of spinal tumors, but the relationship of cellular proliferation with MRI findings for spinal schwannoma is unknown. The subjects were 48 patients (22 males and 26 females) with spinal schwannoma who were classified into three subgroups: iso/homo, high/rim, and hetero/hetero, based on T2WI/contrast T1WI. A retrospective analysis of tumor size and MIB-1 index was performed in the context of these MRI findings. Intraoperative findings and pre- and postoperative motor performance were also examined. The average tumor size was 32.4 mm (range 10-130 mm) and the average MIB-1 index was 3.8% (range 1-12). In the three subgroups, there were no significant differences in sex, age, duration of disease, tumor lesion, and dumbbell type. In the hetero/hetero group, the tumor size was significantly greater and the MIB-1 index was significantly higher (both P < 0.05), than the other two groups. The tumor adherence rate was significantly higher for hetero tumors (P < 0.05) and preoperative paralysis was more common in cases with tumor adhesion. The rate of paralysis improvement at 1 month was significantly lower for hetero tumors, but all cases had improved at 6 months. Contrast T1WI MRI was useful for prediction of the proliferative activity and growth of spinal schwannomas, which are associated with increased tumor size and adhesion. A heterogeneous pattern on contrast T1WI indicated an increase in size and adhesion of the tumor. This pattern reflected the preoperative motor status and postoperative motor recovery. 4.

FEM based evaluation of Fused Layer Modelling monolayers in tensile testing

In a previous work, dumbbell specimens were shown to be inadequate for the tensile testing of Additive Manufacturing monolayers. Finite Element Method (FEM) has been used in this contribution for comparing tensile-stress distributions in both conventional and rectangular samples. Different extrusion paths for the manufacturing via Fused Layer Modelling (FLM) were taken into account. The calculations showed stress concentrations in the dumbbell type specimens in the zone of variable width away from the gauge length. The results were used for explaining the differences between mechanical behavior of dumbbell and rectangular specimens made with FLM from Poly-Lactic Acid (PLA). The mechanical behavior in the experiments closely matches the FEM results. At least 20 % of the tested dumbbell specimens fractured away from the gauge length, compromising the resulting tensile strength data. Rectangular tensile test specimens are proposed as a better alternative.

Topological Structural Stability of Partial Differential Equations on Projected Spaces

In this paper we study topological structural stability for a family of nonlinear semigroups \(T_h(\cdot )\) on Banach space \(X_h\) depending on the parameter h. Our results shows the robustness of the internal dynamics and characterization of global attractors for projected Banach spaces, generalizing previous results for small perturbations of partial differential equations. We apply the results to an abstract semilinear equation with Dumbbell type domains and to an abstract evolution problem discretized by the finite element method.

Genotoxic potential of Fasciolagigantica infection in experimentally infected rabbits.

A number of parasitic platyhelminthes are known to cause genotoxicity in humans and animals. However no such information is available on tropical liver fluke, Fasciola gigantica, which incurs huge economic losses worldwide. In the present study the genotoxic potential of F. gigantica infection in rabbits, experimentally infected with the metacercarial cysts of this parasite, has been investigated using the standard comet assay and micronucleus (MNi) test on the isolated hepatocytes and the whole blood from the infected rabbits. The tail length of the comet in both hepatocytes and reticulocytes from the infected animals was significantly prominent (p<0.05) as compared to the controls. About 61.17% of the hepatocytes from the infected rabbits were positive for MNi formation. A number of blood cells also showed cellular deformities, which were recognised as spicule type, schistocytes, tear drop type, acanthocytes and dumbbell type. It is possible that during the establishment of host-parasite relationship the worms might have released some products which could have contributed to the induction of cellular and DNA damage. However, long term studies are required to understand the serious implications of such an effect caused by F. gigantica, though hepatic carcinoma has not been reported so far due to fasciolosis, however, considering the present results the possibility may not be rule out for the disease progression in this direction.

On super edge-magic deficiency of volvox and dumbbell graphs

Let G=(V,E) be a finite, simple and undirected graph of order p and size q. A super edge-magic total labeling of a graph G is a bijection λ:V(G)∪E(G)→{1,2,…,p+q}, where the vertices are labeled with the numbers 1,2,…,p and there exists a constant t such that f(x)+f(xy)+f(y)=t, for every edge xy∈E(G). The super edge-magic deficiency of a graph G, denoted by μs(G), is the minimum nonnegative integer n such that G∪nK1 has a super edge-magic total labeling, or it is ∞ if there exists no such n.In this paper, we are dealing with the super edge-magic deficiency of volvox and dumbbell type graphs.

MEMS thermal flow sensors

This paper presents micromachined thermal flow sensors for measuring liquid flow down to 0.05μl/min. The sensing element is a parylene-C thin film with two thin film platinum resistors as heating and sensing elements. The sensors are integrated with AWG 24 Teflon tubing and additional two external constant resistors to form a Wheatstone bridge. In this study, we investigated the efficacy of the orifice type sensor in two configurations, vertical and horizontal. In vertical configuration, the sensor was arranged perpendicular to the flow direction. The orifice flow allows maximum heat transfer from the sensor to the flow but leads to higher flow resistance. After redesigning the geometries of the sensor, the dumbbell type thermal flow sensor was further developed. The sensor is suspended in the middle of the channel to improve thermal insulation and achieve better sensitivity. The sensors have demonstrated a flow rate resolution below 0.05μl/min. The experimental results show that the sensor has a sensitivity of 7.7mV/(μl/min) at 0.13mW power consumption and 0.05μl/min volumetric flow rates. Comparison with related literature has been made to judge how good the flow sensors developed in this study are.

Fabrication of Microspheres Based on Poly(4-butyltriphenylamine) Blends with Poly(methyl methacrylate) and Block Copolymer by Solvent Evaporation Method

Micron-sized polymer particles from single poly(4-butyltriphenylamine) (PBTPA) homopolymer, binary polymer blend [PBTPA/poly(methyl methacrylate) (PMMA)], and ternary polymer blend (PBTPA/PBTPA-b-PMMA/PMMA) via a solvent evaporation method, and the surface morphologies and inside structure of resulting particles were investigated. Spherical homopolymer particles with smooth surface were resulted from PBTPA with low molecular weight. In the case of binary blends (PBTPA/PMMA = 1/1), Janus (low molecular weight) and dumbbell (high molecular weight) type morphologies were observed. The particles based on ternary blends containing PBTPA-b-PMMA showed core-shell type morphologies (PMMA; core, PBTPA; shell). Degree of engulfment of PMMArich domain increased with the content of the block copolymer. The decrease of domain size was not observed although the block copolymer had a suitable structure as a compatibilizer for the blend. It was also found that the initial concentration of polymer solution had an effect on the final morphology.

Coefficient of restitution of aspherical particles.

We consider the motion of an aspherical inelastic particle of dumbbell type bouncing repeatedly on a horizontal flat surface. The coefficient of restitution of such a particle depends not only on material properties and impact velocity but also on the angular orientation at the instant of the collision whose variance is considerable, even for small eccentricity. Assuming random angular orientation of the particle at the instant of contact we characterize the measured coefficient of restitution as a fluctuating quantity and obtain a wide probability density function including a finite probability for negative values of the coefficient of restitution. This may be understood from the partial exchange of translational and rotational kinetic energy.

Defect structures induced by high-energy displacement cascades in γ uranium

Displacement cascade simulations were conducted for the γ uranium system based on molecular dynamics. A recently developed modified embedded atom method (MEAM) potential was employed to replicate the atomic interactions while an embedded atom method (EAM) potential was adopted to help characterize the defect structures induced by the displacement cascades. The atomic displacement process was studied by providing primary knock-on atoms (PKAs) with kinetic energies from 1keV to 50keV. The influence of the PKA incident direction was examined. The defect structures were analyzed after the systems were fully relaxed. The states of the self-interstitial atoms (SIAs) were categorized into various types of dumbbells, the crowdion, and the octahedral interstitial. The voids were determined to have a polyhedral shape with {110} facets. The size distribution of the voids was also obtained. The results of this study not only expand the knowledge of the microstructural evolution in irradiated γ uranium, but also provide valuable references for the radiation-induced defects in uranium alloy fuels.

비정질 강섬유보강콘크리트의 구속건조수축균열 특성

In this study, free and restraint drying shrinkage tests of conventional and amorphous steel fiber-reinforced concrete were performed to investigate the shrinkage characteristics. To consider the effect of restraint condition of concrete on shrinkage cracking, three different test setups were used: ring type restraint test according to ASTM C 1581-04, dumbbell type restraint test according to KS F 2595, and modified dumbbell type restraint test with notches. Crack widths and strain profiles acquired from the tests were compared and investigated. The test results showed that the addition of amorphous steel fibers with 0.2-0.4% volume fraction into concrete resulted in 30% reduction of free drying shrinkage, 3-5 days delay of crack development time, and 20-60% reduction of crack width. Thus, it can be concluded that the amorphous steel fibers can be used for the purpose of crack control of concrete shrinkage cracking.

Strain Rate Effects on Strain-Induced Martensitic Transformation and Electrical Resistivity of Deforming Stainless Steel

Austenitic stainless steel was compressed at a strain rates of 103 s-1 using a Hopkinson pressure bar apparatus at temperatures of 77 K and 293 K. The electrical resistivity was measured to determine the volume fraction of martensite of a deforming specimen. A compressive specimen of the dumbbell type was suitable for attaching the lead-in wires of four-point probes to the specimen. The volume fraction of martensite formed at a strain rate of 103 s-1 was lower than that formed at a low strain rate regardless of the temperature, and the effect of the strain rate on the electrical resistivity was slight. However, since the volume fraction of martensite is expressed as a linear function of the electrical resistivity ratio as well as in the results obtained by the tensile test, the electrical resistivity was available as an index for estimating the volume fraction of martensite induced by dynamic deformation. The duration of the input wave was approximately 150 μs, and the appearance of the peak value of transient resistivity was approximately 1ms after the arrival of the input wave at the specimen. These results showed that the structure change evaluated using electrical resistivity was not completed in the time required for the stress wave to pass through the specimen, although the electrical resistivity immediately after dynamic deformation closely approached that obtained by the static test.

Cervical Symmetric Dumbbell Ganglioneuromas Causing Severe Paresis

We report an extremely rare case with bilateral and symmetric dumbbell ganglioneuromas of the cervical spine in an elderly patient. A 72-year-old man came by ambulance to our hospital due to progressive incomplete paraplegia. Magnetic resonance imaging demonstrated bilateral symmetric dumbbell tumors at the C1/2 level. We performed total resection of the intracanalar tumor, aiming at complete decompression of the spinal cord, and partial and subtotal resection of foraminal outside portions. Histopathological examination of the surgical specimen indicated the tumor cells to be spindle cells with the presence of ganglion cells and no cellular pleomorphism, suggesting a diagnosis of ganglioneuroma. Although the surgery was not curative, the postoperative course was uneventful and provided a satisfactory outcome. This is the fourth known case of cervical ganglioneuromas of the bilateral symmetric dumbbell type.

Clinical efficacy of surgical treatment for hilar cholangiocarcinoma: a report of 207 cases

Objective To investigate the efficacy of different radical surgical procedures for the treatment of hilar cholangiocarcinoma.Methods The clinical data of 207 patients with hilar cholangiocarcinoma who were treated at the Southwest Hospital from June 2007 to June 2012 were retrospectively analyzed.Local resection or hemihepatectomy combined with caudate lobectomy was applied to patients with Bismuth type Ⅰ hilar cholangiocarcinoma; dumbbell type radical resection was applied to patients with Bismuth type Ⅱ hilar cholangiocarcinoma or some patients with type Ⅲ a,Ⅲ b and Ⅳ hilar cholangiocarcinoma; hemihepatectomy or extended hemihepatectomy combined with caudate lobectomy was applied to patients with Bismuth type Ⅲ a,Ⅲ b and Ⅳ hilar cholangiocarcinoma.The patients were followed up every 3 months postoperatively till December 2012.All data were analyzed using the chi-square test or Fisher exact probability test,the survival curve was drawn by Kaplan-Meier method,and the survival was analyzed using the Log-rank test.Results Of the 207 patients,124 received radical resection,including 14 received local resection,23 received dumbbell type resection,87 received lobectomy + caudate lobectomy,49 received palliative resection; 34 received biliary drainage.Four patients died perioperatively.The incidences of complications of dumbbell type radical resection,left hemihepatectomy + caudate lobectomy,right hemihepatectomy + caudate lobectomy were 21.7％ (5/23),46.6％ (27/58) and 48.3％ (14/29),respectively.The incidence of complications after dumbbell type radical resection was significantly lower than left hemihepatectomy + caudate lobectomy and right hemihepatectomy + caudate lobectomy (x2 =4.42,3.90,P ＜ 0.05).One hundred and seventy patients were followed up.The median survival time of the 112 patients who received radical radical resection was 26.5 months,and the 1-,3-,5-year survival rates were 75.9％ (85/112),42.9％ (24/56) and 28.9％ (11/38),respectively.The median survival time of the 38 patients who received palliative resection was 8.5 months,and the 1-,3-year survival rates were 31.6％ (12/38) and 0.The survival time of 20 patients who received biliary drainage was 4.0 months,and the l-year survival rate was 0.The survival rate of patients who received radical resection was significantly higher than those who received palliative resection (x2=65.32,P ＜ 0.05).There was a significant difference in the survival rate between patients who received surgical treatment and those who received biliary drainage (x2=99.97,P ＜ 0.05).Of the 112 patients who received radical resection,the median survival time of 10 patients who received local resection of tumor was 47.0 months,the 1-year survival rate was 10/10,and 4 patients survived at the end of the follow-up; the median survival time of 23 patients who received dumbbell type radical resection was 32.0 months,and the 1-,3-year survival rates were 95.7％ (22/23) and 7/15,and the survival time of 6 patients was longer than 5 years; the median survival time of 54 patients who received left hemihepatectomy or extended left hemihepatectomy + caudate lobectomy was 27.6 months,and the 1-,3-year survival rates were 42.1％ (24/57) and 38.7％ (12/32),and the survival time of 9 patients was longer than 5 years,3 patients survived at the end of the follow-up ; the median survival time of 25 patients who received right hemihepatectomy or extended right hemihepatectomy + caudate lobectomy was 28.3 months,and the 1-,3-year survival rates were 45.8％ (11/24) and 6/15,and the survival time of 6 patients was longer than 5 years,2 patients survived at the end of follow-up.The median survival time of 35 patients (patients with Bismuth type Ⅰ,Ⅱ hilar cholangiocarcinoma and Bismuth Ⅲ a and Ⅲ b hilar cholangiocarcinoma which did not invade the secondary bile duct) who received hemihepatectomy + caudate lobectomy was 32.0 months,and the 1-,3-,5-year survival rates were 91.4％ (32/35),45.8％ (11/24) and 5/16,which were not different from the survival rate of patients who received dumbbell type radical resection (x2 =0.17,P ＞ 0.05).The 5-year survival rate of patients with lymph node metastasis was 4/19,which was significantly lower than 30.4％ (7/23) of patients without lymph node metastasis (x2 =23.40,P ＜ 0.05).Conclusion Joint lobectomy and standardized lymph node dissection could help to improve the efficacy of surgical treatment for patients with hilar cholangiocarcinoma. Key words: Biliary neoplasms, hilar; Radical resection ; Efficacy