Dumbbell Form Research Articles

THE EFFECT OF REPETITIVE METAL CASTING ON THE TENSILE STRENGTH OF DENTURES

Background: Dentures or prostheses function to replace chewing and dental arch structures. Denture plates used in dentistry are made with acrylic resin, metal, or a combination of acrylic and metal. Metals are shiny, opaque chemical substances and good conductors of heat and can be polished. Recycling or reusing used metal is an option in making prostheses because the price of new metal is increasing, and metal recycling is quite effective. Purpose: To determine the effect of repeated metal casting on the strength of the metal frame denture base. Method: The current research is a laboratory study with a tensile test in the form of dumbbells with iso 22674 with a length of 15 ± 1 mm and a diameter of 3 ± 1 mm. This research used 18 CoCr metal samples divided into three groups, namely 100% new metal group (control), 50% new + 50% repeated composition group, and 100% repeated group. Result: The mean strain of the new 100% CoCr metals group was 0.133%, strain mean of the new 50% CoCr + 50% repeated metals group was 0.1%, and the strain of the 100% repeated CoCr metals group was 0.066%. The average modulus of elasticity (MPa) for the new 100% CoCr metals group is 7866, or 711 MPa, the new 50% CoCr + 50% repeat metals group is 7538, or 833 MPa, the 100% CoCr metals group is 6659, or 336 MPa. Conclusion: The new 100% CoCr metal group has a higher average tensile strength value than the 50% new CoCr metal + 50% repeated group, and the lowest is the 100% repeated CoCr metal group.

Manipulation of ionic transport behavior in smart nanochannels by diffuse bipolar soft layer

Soft bipolar nanochannels provide distinct and valuable understanding of the intricate relationship among shape, charge distribution, concentration, and flow dynamics. This study investigates the intriguing realm of nanoscale structures, where two distinct configurations of soft layers with varying charges provide an intricate but appealing setting for the movement and management of ions, as well as the regulation and control of ionic species in nanochannels with five various geometries. It generates cylindrical, trumpet, dumbbell, hourglass, and conical forms. The nanochannels are coated with a diffuse polyelectrolyte layer, and the charge density distribution in the soft layer is described using the soft step distribution function. To enhance accuracy, the impact of ionic partitioning is taken into account. To investigate the effect of soft layer polarity, two types were considered: Type I and Type II. In Type I, the negative pole is at the start, while in Type II, the positive pole is at the start. Thus, Type I features a bipolar soft layer arrangement of negative–positive (NP), whereas Type II has a positive–negative (PN) configuration. The research was conducted under stationary conditions using the finite element method, Poisson–Nernst–Planck, and Navier–Stokes equations. By manipulating variables such as the arrangement order, charge density of the soft layer, and bulk concentration, a numerical analysis was performed to investigate the impact of these variables on current–voltage parameters. The results demonstrate the soft layer with a positive charge serves as a more effective receiver layer for generating greater rectification. For instance, the dumbbell-shaped nanochannel exhibits a rectification of 2046 at a concentration of 1 mM and the lowest charge density in the soft layer. From an alternative perspective, the conductivity in bipolar nanochannels is significantly influenced by the bulk concentration. The study's findings on the fundamental principles of soft bipolar nanochannels have profound implications for the diverse applications of nanochannels. The capacity to regulate and manipulate ion transport through these nanochannels can result in enhanced efficiency, selectivity, and performance in various processes.

Effect of local chemical environment on the point defects in AlNbTiZr refractory high entropy alloys

The effect of local chemical environment (i.e., type and content of atom neighboring to defects) on the point defect properties has been thoroughly investigated in bcc AlNbTiZr refractory high-entropy alloys (HEAs). It has been shown that the randomness of local chemical environments in AlNbTiZr HEAs leads to a wide distribution of vacancy and interstitial formation energy rather than to definitive values. One interesting aside here is that the number of Al and Nb atoms locating at the first-nearest neighbor (1nn) of vacancy drives the evolution of vacancy formation energy (VFE) in AlNbTiZr system, as vacancies preferred Al-rich and Nb-poor environments. What another worth noticing is that the most stable interstitial defects are in the form of dumbbells. What's more, the Al-Al dumbbell is the easiest interstitial defect while the Zr-Zr dumbbell is the least according to the lowest formation energy and electronic characteristics. Along with the results of vacancies preferred Al-rich environments, Al in AlNbTiZr can stabilize the single vacancy and inhibit its migration and diffusion to form large-size vacancy clusters. Therefore, the initial irradiation resistance can be improved by adjusting the concentration and distribution of Al in AlNbTiZr. One can infer from the results obtained present that it is beneficial in improving the irradiation resistance by controlling different processing experimentally methods to increase the occurrence of Al-Al arrangement in AlNbTiZr high-entropy alloys.

Analysis and optimization of transient heat dissipation characteristics of high power resistors with a sensible heat storage method

The load voltage of the resistor will rise sharply when there is a control imbalance or short circuit in the circuit, and the resistance wire will fuse in a matter of seconds, causing the resistor to burn. Designing resistors with superior transient heat dissipation capabilities is therefore crucial. In this work, using sensible heat storage, various sizes of iron rods are developed and inserted into the ceramic to enhance heat transfer by utilizing iron’s high thermal conductivity. In addition, to maximize the material’s high thermal capacity for heat storage, ceramic blocks in the form of dumbbells were also put between the ceramic rods inside the resistor. The results demonstrated that both designs could enhance the resistor’s capability to dissipate heat. When iron rods with a diameter of 7 mm are inserted, the device’s capacity for heat storage is raised by 19.09 %, and its heat storage efficiency increases by 16.24 %. The device’s capacity for heat storage can be raised by 20.5 %, and its heat storage efficiency can be raised by 18.23 % by embedding a ceramic dumbbell with a 9 mm diameter.

An increase of the mechanical strength and hardness of polymeric materials radiation-crosslinked by X-ray radiation from an gaseous electric discharge

The problem of investigation of mechanical and electrophysical properties of polymeric materials crosslinked by X-ray radiation from a gaseous electric discharge is considered. The effect of radiation crosslinking on the mechanical strength and hardness of polymers is presented by the example of samples of various thicknesses (from 0.08 mm to 10 mm) of LDPE and HDPE made using crosslinking technology by X-ray radiation from a barrier gaseous electric discharge proposed in [1]. Experimental data obtained on samples of low molecular weight LDPE-107-02K and high molecular weight HDPE-271-82K made in the form of dumbbell, cut in accordance with GOST IEC 60811-2-1 from PE plates, are considered. To study the electrophysical properties and the depth of semi-absorption of X-ray radiation from gaseous electric discharge, LDPE and HDPE samples in the form of disks of different thicknesses were used.The depth of penetration of X-ray radiation from a gaseous discharge into LDPE-107-02K and HDPE-271-82K was estimated.Comparative studies of changes in the electrophysical properties of mechanical strength and hardness of cable LDPE under the influence of X-ray radiation from gaseous discharge and under the influence of an electron beam are carried out.It is shown that the mechanical strength and hardness of LDPE and HDPE can be increased by at least 30% and 60% respectively via radiation crosslinking by X-ray from a gaseous discharge.

Combined approach for cervical schwannomas with large extraforaminal extension

Background Data : About 75% of Spinal schwannoms are intradural, 10%intra-extradural and 15% are completely extradural . These tumors are usually slowly growing and reach a large size before becoming symptomatic. The tumors which are totally or partially located in the epidural space (dumbbell tumors) are either intraspinal, foraminal or extraspinal. These dumbbell forms represent about 18 % of the total percentage of whole spinal schwannomas, but they are responsible for almost half of the cervical schwannomas When these tumors have large extraforaminal part it become so difficult to achieve total excision through a single approach . Study design : This is a retrospective study. Purpose: To evaluate the efficacy and safety of combined approach for excision of these large tumors closely related to the vertebral artery Patients and Methods : This study was conducted in Mansoura University Hospital on 6 patients two males and four females their age ranged (22-50) years with cervical spinal schwannoms with large lateral extra formaninal component. All patients were assessed clinically and radiologically using CT and MRI cervical spine and vertebral artery angiography before surgery. Posterior approach through a hemilaminectomy with facet preservation was used for excision of the intraspinal part without disturbing the cervical spine stability and with limited postoperative neck pain and a lateral approach for excision the extraspinal extension to avoid so much manibulation on the vertebral artery. Follow up MRI cervical spine was done postoperatively for follow up. Results : Combined approach was done for all patients with complete excision of the tumors . One patient developed CSF Leake after surgery that stopped after lumbar drain insertion . There was no mortality in this study. Conclusion : Cervical spinal schwannoms with large lateral extra formaninal component need combined approach to achieve complete surgical excision , avoid vertebral artery injury and preserve stability .

Effect of particles with repulsive interactions enclosed in both rigid spherical shells and flexible fluid vesicles studied by Monte Carlo simulation.

Experimental observations indicate that the repulsion of particles is a factor that induces the transformation of vesicles containing multiple particles. Metropolis Monte Carlo simulations are performed with two models in which repulsive particles are enclosed inside a vesicle. The distribution of the particles and the effective bending coefficient and surface tension of the membrane are analyzed. The shape and internal structure of the vesicle containing the particles are investigated as the vesicle volume is decreased. It is revealed that the repulsive interaction between particles produces a layered structure and stiffens the membrane. When particles repulsively interact over a long range, the membrane takes on a dumbbell form.

Cyclodextrin-Sandwiched Hexaphyrin Hybrids: Side-to-Side Cavity Coupling Switched by a Temperature- and Redox-Responsive Central Device.

Access to allosteric enzyme mimics that ideally associate communicating compartments for catalysis and regulation is still challenging. Whereas a sandwich "cavity-catalyst-cavity" approach, developed mainly with cyclodextrins and porphyrins, appears promising, its counterpart with hexaphyrins featuring rich conformation, aromaticity, and coordination behavior has not been prospected at all. We thus developed sandwich hybrids made of two cyclodextrins triply linked on each side of a hexaphyrin. The latter displays switchable oxidation states with interconvertible conformations (28π antiaromatic and 26π aromatic, each adopting rectangular and dumbbell forms). These four states are connected by two orthogonal switches under redox [aromaticity] and thermal [shape] control. This leads to twin compartmentalized confined spaces either locked or unlocked depending on the conformation of the hexaphyrin, and the reversibility of the lock↔unlock transition relies on the aromaticity of the hexaphyrin. The sandwiched heteroannulene thus behaves as an unprecedented dual-responsive double-latched device. Such hybrid systems open interesting perspectives in the allosteric regulation of receptors, catalysts, and machineries.

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.

A comparison of amorphous calcium carbonate crystallization in aqueous solutions of MgCl2 and MgSO4: implications for paleo-ocean chemistry

Based on the terminology of “aragonite seas” and “calcite seas”, whether different Mg sources could affect the mineralogy of carbonate sediments at the same Mg/Ca ratio was explored, which was expected to provide a qualitative assessment of the chemistry of the paleo-ocean. In this work, amorphous calcium carbonate (ACC) was prepared by direct precipitation in anhydrous ethanol and used as a precursor to study crystallization processes in MgSO4 and MgCl2 solutions having different concentrations at 60 °C (reaction times 240 and 2880 min). Based on the morphology of the aragonite crystals, as well as mineral saturation indices and kinetic analysis of geochemical processes, it was found that these crystals formed with a spherulitic texture in 4 steps. First, ACC crystallized into columnar Mg calcite by nearly oriented attachment. Second, the Mg calcite changed from columnar shapes into smooth dumbbell forms. Third, the Mg calcite transformed into rough dumbbell or cauliflower-shaped aragonite forms by local dissolution and precipitation. Finally, the aragonite transformed further into spherulitic radial and irregular aggregate forms. The increase in Ca2+ in the MgSO4 solutions compared with the MgCl2 solutions indicates the fast dissolution and slow precipitation of ACC in the former solutions. The phase transition was more complete in the 0.005 M MgCl2 solution, whereas Mg calcite crystallized from the 0.005 M MgSO4 solution, indicating that Mg calcite could be formed more easily in an MgSO4 solution. Based on these findings, aragonite and Mg calcite relative to ACC could be used to provide a qualitative assessment of the chemistry of the paleo-ocean. Therefore, calcite seas relative to high-Mg calcite could reflect a low concentration MgSO4 paleo-ocean, while aragonite seas could be related to an MgCl2 or high concentration of MgSO4 paleo-ocean.

Distinct immunological activation profiles of dSLIM® and ProMune® depend on their different structural context.

IntroductionDNA‐based TLR9 agonists are potent activators of the immune system. ProMune® and dSLIM® belong to different families of TLR9 agonists and both have been established as cancer immunotherapeutics in clinical proof‐of‐concept studies. Unfortunately, ProMune® failed in pivotal oncological trials. dSLIM®, the active ingredient of Lefitolimod (MGN1703), successfully finished a double‐blinded, placebo‐controlled phase II study in patients with advanced colorectal cancer, exhibiting improved progression‐free survival and durable disease control.MethodsTo explain the different systemic efficacies of dSLIM® and ProMune®, both TLR9 agonists and chimeric molecules thereof are analyzed side‐by‐side in a panel of in vitro assays for immune activation.Results and conclusionsIndeed, dSLIM® exposure results in an IFN‐α dependent broad activation of immune cells whereas ProMune® strongly stimulates B cells. Moreover, all functional effects of dSLIM® strictly depend on the presence of CG‐motifs within its dumbbell‐shaped, covalently closed structural context. Conversely, several immunological effects of ProMune® like IL‐8 secretion are independent of CG‐motifs and could be ascribed to the phosphorothioate‐modifications of its DNA backbone, which may have caused the side effects of ProMune® in clinical trials. Finally, we showed that the implementation of ProMune® (ODN2006) base sequence into the characteristic dSLIM® dumbbell form resulted in dSLIM2006 with all beneficial effects for immunostimulation combined from both TLR9 classes without any CG‐independent effects.

Aerodynamic drag from two tubes in side-by-side arrangement for different tube shapes

Experimental investigations of aerodynamic drag from two tubes in side-by-side arrangement for different tube shapes in the range of Reynolds numbers from 4000 to16000 are performed. Comparison of experimental data is executed. It is set, that the tubes of drop-shaped form have less aerodynamic drag and the tubes of flat-oval and dumb-bell forms have greater drag as compared to drag of circular tubes

GeAs: Highly Anisotropic van der Waals Thermoelectric Material

GeAs and Sn-doped GeAs were synthesized from elements. Both crystallize in a layered crystal structure in the C2/m space group (No. 12) in the GaTe structure type. The crystal structure consists of As-terminated layers separated by van der Waals gaps. 119Sn Mossbauer spectroscopy reveals that in the doped compound, Sn atoms are situated in a symmetric and homogeneous environment, most probably in the form of Sn2 dumbbells. The anisotropic crystal structure of GeAs leads to highly anisotropic transport properties. High electrical and thermal conductivities were determined along the crystallographic layers. For the perpendicular direction across the layers, a sharp drop of more than an order of magnitude was observed for the transport properties of the GeAs single crystal. As a result, an order of magnitude difference in the figure of merit, ZT, was achieved. High-temperature thermoelectric characterization of the Sn-doped compound reveals a remarkable ZT with a maximum of 0.35 at 660 K.

Planar oscillations of a dumb-bell of a variable length in a central field of Newtonian attraction. Exact approach

Dynamics of a dumb-bell of a variable length in a central field of Newtonian attraction is considered. It is assumed that the body moves in a plane fixed in the absolute space and passing through an attracting center. The law of length׳s variation providing an existence of stationary configurations is pointed out. For these configurations the dumb-bell forms a constant angle with a local vertical passing through the center of mass of the dumb-bell, which moves in an elliptic orbit similar to the Keplerian. In particular, the mentioned constant angle may be equal to zero. In contrast to previous investigations (Burov and Kosenko, 2011 [8,10], Burov, 2011 [9]) the problem is solved within the exact formulation, without supplementary simplifying assumptions concerning smallness of the dumb-bell in comparison to its distance from the attracting center.

Study of various Sb2S3 nanostructures synthesized by simple solvothermal and hydrothermal methods

Controlling the size and morphology of the antimony sulfide nanostructures is important for photocatalytic and photovoltaic applications. Herein, we report a systematic approach to synthesize various nanostructures of antimony sulfide. Based on simple solvothermal and hydrothermal routes antimony sulfide nanorods have been synthesized at different temperatures. The size of the nanorods and the morphology of the constituent nano-units, in the form of nanorods, dumbbell and sphere have been controlled by adjusting the temperature. The changes have been confirmed by scanning electron microscope and transmission electron microscope analysis.

Vplyv plyometrického tréningu na zmeny silových schopností vrcholových volejbalistiek

The aim two groups time parallel 6-week experiment was to compare selected types of plyometric training. One group trained with gradation of external weight loading in eccentric phase (EXP1) and the second group increased drop height (EXP2) during drop jump training. We compared their effects on changes in selected strength abilities. We assessed the level of countermovement vertical jump height (CMJ), standing vertical jump height (SJ) and average force gradient in squat exercises with the knee joint in 90 ° by maximal isometric contraction at intervals of 0-50 ms (RFD50) and 0-200 ms (RFD200). The results showed that in CMJ EXP1 had improved by 1.01 cm (3.5%) (p<0.01). EXP2 improved by an average of 1.78 cm (5.5 %) (p<0.05). SJ in EXP1 average improved by 0.94 cm (3.5 %) (p = n.s.) in EXP2 by 1.91 cm (6.6 %) (p<0.05). In RDF50 the average increase observed after a period of training in EXP1 1.03 N.ms-1 (26.08 %) (p = n.s.) and EXP2 0.57 N.ms-1 (16.39 %) (p<0.05). In the EXP1 RFD200 the average increase was 2.51 N.ms-1 after a period of training (20.91 %) (p<0.01), while on average EXP2 improved by 1.05 N.ms-1 (10.04 %) (p = n.s.). Based on these results we recommend to improving of vertical jump height with a countermovement and force gradient in longer intervals (200 ms) to apply the external weight in the form of small dumbbells in eccentric phase of drop jump training. To standing jump height development and shorter time intervals of force gradient (50 ms) is recommended to use a gradual increase in height of drop in plyometric training.

Self-Assembled Monolayers on Au(111): Structure, Energetics, and Mechanism of Reconstruction Lifting

Density-functional theory calculations are used to compare competing structural models for SH molecules on Au(111) and to explain the effect of the adsorbed molecules on the energetics of surface reconstruction. Our results indicate that dumbbells, formed by binding two SH molecules to an adatom, are energetically stable structures at low and intermediate coverages, while the recently proposed c(4 × 2) structure with partial occupancies for adatom and vacancy sites [A. Cossaro et al., Science2008, 321, 943] is preferred at full coverage. Lifting of the Au(111) herringbone reconstruction is attributed to reduction of surface stress due to outward in-plane relaxations of surface Au atoms under the adsorbed species. The smallest reduction of surface stress per molecule occurs when SH molecules are adsorbed in the form of dumbbells, while isolated adatoms and SH molecules have similar effects on the surface stress and reconstruction energy. SH molecules are predicted to energetically favor the fcc region of t...

High Sensitivity Surface-Enhanced Raman Scattering in Solution Using Engineered Silver Nanosphere Dimers

We describe Raman spectroscopy measurements of distyrylbenzene (DSB) molecules equipped with plasmonic antennae in the form of silver dumbbells in aqueous solution under ambient conditions. A synthetic strategy in which the dithiolated molecule is used as the linker between silver nanospheres ensures that the molecules are attached at the intersphere gap where local fields are maximally enhanced. The measured and calculated enhancement factors are in excellent agreement. The reported method has sufficient sensitivity to also allow for the detection of molecules tethered to single spheres, with 100–1000-fold weaker enhancement. Spectral analysis allows assignment of structures and reveals that in addition to the normal Raman active modes IR active transitions appear in the Raman spectra where field gradients dominate.

Phytochrome three-dimensional structures and functions

The complete three-dimensional sensory module structures of the Pr ground state of Synechocystis 6803 Cph1 and the unusual Pfr ground state of the bacteriophytochrome PaBphP (PDB codes 2VEA and 3C2W respectively) have now been solved, revealing an asymmetrical dumbbell form made up of a PAS (Period/ARNT/Singleminded)-GAF (cGMP phosphodiesterase/adenylate cyclase/FhlA) bidomain carrying the chromophore and the smaller PHY (phytochrome-specific) domain. The PHY domain is structurally related to the GAF family, but carries an unusual tongue-like structure which contacts the larger lobe to seal the chromophore pocket. In 2VEA, the tongue makes intimate contact with the helical N-terminus; both the N-terminus and the tongue structures are quite different in 3C2W. As expected, the structures reveal ZZZssa and ZZEssa chromophore conformations in 2VEA and 3C2W respectively, associated with tautomeric differences in several nearby tyrosine residues. Two salt bridges on opposite sides of the chromophore, as well as the associations of the C-ring propionates also differ. It is still unclear, however, which of these structural differences are associated with bacteriophytochromes compared with Cph1 and plant-type phytochromes, the unusual 3C2W Pfr ground state functionality compared with the Pr ground state or the Pr compared with Pfr photoisomerism. To access the latter unambiguously, both Pr and Pfr structures of the same molecule are required. New solid-phase NMR data for Cph1 in the Pr, Pfr and freeze-trapped intermediate states reveal unexpected changes in the chromophore during Pfr-->Pr photoconversion. These, together with our efforts to solve the three-dimensional structure of a complete phytochrome molecule are also described.

Calcium carbonate precipitation induced by a bacterium strain isolated from an oligotrophic cave in Central China

A heterotrophic Bacillus sp. strain (5C-1) was isolated from Heshang cave, an oligotrophic karst cave in the middle reaches of Yangtze River, and identified by BIOLOG and 16S rDNA sequencing. Bacterially induced formation of calcium carbonate by 5C-1 was investigated in several comparative experimental sets with or without the cell and extracellular enzymes. The temporal variations of both the amount of the precipitates and the pH values of the solution were measured by a spectrophotometer and a pH meter, respectively. The morphological characteristics of the calcium carbonate precipitates were observed with environmental scanning electronic microscopy (ESEM). The growth of 5C-1 was found to greatly promote the pH value of the liquid medium in the first 2 days, which favors the formation of calcium carbonate. No precipitates were formed with the pH value lower than 8.6, though the pH value was demonstrated to be not the only factor controlling the formation of the calcium carbonate. The accumulation of extracellular polysaccharide substance was observed to favor the precipitate formation. Only when both factors reached a threshold did the precipitates form with the addition of CaCl2. Cells and extracellular enzymes were not the factors that limit the precipitate formation in our microbial systems. The precipitates of a variety of morphological features including dumb bells, peanuts, irregular and spherical and rhombic forms were mainly observed in our microbial systems but not in the chemical control system. Interestingly, imprints of bacter- ial cells and spores were observed to be present on the surface of the precipitates of a peanut or a dumb bell form, probably indicative of the microbial escaping mechanism during the mineralization of calcium carbonate.