Plastic Shell Research Articles

Effects of Constant Flickering Light on Refractive Status, 5-HT and 5-HT2A Receptor in Guinea Pigs

PurposeTo investigate the effects of constant flickering light on refractive development, the role of serotonin (i.e.5-hydroxytryptamine, 5-HT)and 5-HT2A receptor in myopia induced by flickering light in guinea pigs.MethodsForty-five guinea pigs were randomly divided into three groups: control, form deprivation myopia (FDM) and flickering light induced myopia (FLM) groups(n = 15 for each group). The right eyes of the FDM group were covered with semitransparent hemispherical plastic shells serving as eye diffusers. Guinea pigs in FLM group were raised with illumination of a duty cycle of 50% at a flash frequency of 0.5Hz. The refractive status, axial length (AL), corneal radius of curvature(CRC) were measured by streak retinoscope, A-scan ultrasonography and keratometer, respectively. Ultramicroscopy images were taken by electron microscopy. The concentrations of 5-HTin the retina, vitreous body and retinal pigment epithelium (RPE) were assessed by high performance liquid chromatography, the retinal 5-HT2A receptor expression was evaluated by immunohistofluorescence and western blot.ResultsThe refraction of FDM and FLM eyes became myopic from some time point (the 4th week and the 6th week, respectively) in the course of the experiment, which was indicated by significantly decreased refraction and longer AL when compared with the controls (p<0.05). The concentrations of 5-HT in the retina, vitreous body and RPE of FDM and FLM eyes were significantly increased in comparison with those of control eyes (both p<0.05). Similar to FDM eyes, the expression of retinal 5-HT2A receptor in FLM eyes was significantly up-regulated compared to that of control eyes (both p<0.05). Western blot analysis showed that retinal 5-HT2A receptor level elevated less in the FLM eyes than that in the FDM eyes. Moreover, the levels of norepinephrine and epinephrine in FDM and FLM groups generally decreased when compared with control groups (all p<0.05).ConclusionsConstant flickering light could cause progressive myopia in guinea pigs. 5-HT and 5-HT2A receptor increased both in form deprivation myopia and flickering light induced myopia, indicating that 5-HT possibly involved in myopic development via binding to5-HT2A receptor.

On the reality of local and ecological races in lymnaeid snails (Mollusca, Gastropoda, Lymnaeidae)

The reality of ecological and local races was investigated in two widespread Palearctic species of lymnaeid snails (Lymnaea stagnalis and Radix auricularia). Several methods of statistical analysis were used, including two-way ANOVA, cluster analysis, and discriminant analysis for six plastic shell characters. It was shown that none of the methods used could convincingly demonstrate that ecological and local races were present in the studied species. Even in cases when statistically significant differences among the populations in the morphology of shells were revealed, these differences were very small and did not correspond to the meaning that was put into the concept of “race” by malacologists in the past. Perhaps, the formation of such races in pond snails is possible only in case of populations being formed in suboptimal conditions, for example, in thermal springs or at large depths. This being the case, the distinguishing of races requires using other shell characters, both quantitative and qualitative ones.

Image features of lens opacity in pediatric cataracts using ultrasound biomicroscopy

To study lens opacity in pediatric cataract images captured using ultrasound biomicroscopy (UBM). The medical records of patients operated on from September 2012 to October 2013 were reviewed retrospectively. Prior to surgery, patients were placed in the supine position under sedation with oral chloral hydrate for UBM imaging. Lens morphology was evaluated by UBM examination with a 50MHz probe that was equipped with a water bag instead of the standard plastic shell. UBM images were compared to images captured from intraoperative videos. UBM examination was performed in 50 patients (including 10 infants) aged 2months to 6years. The UBM ecographic images showed features specific to pediatric cataract lenses. These features were used to define 2 types of anterior capsule of the lens, 4 types of cortex and nucleus of the lens, 3 types of posterior capsule of the lens, and membranous cataracts. Capsule morphology and the cortex density of pediatric cataracts could be evaluated before surgery using UBM imaging. Adoption of this technique could provide useful preoperative information to surgeons.

Take a Good Lamp

Revital Cohen and Tuur Van Balen (www.cohenvanbalen.com) have investigated the multiple materialities, modes of production, and long networks of contemporary technological culture in many of their installation and film works. This has ranged from work with bioengineering (Sterile) to work with the rare earth minerals and metals that form the backbone of contemporary media. In works such as H/AlCuTaAu and the later D/AlCuNdAu, they remediated the existing chemical elements of electronics and data centers into an odd sort of hybrid art-installation object; in 75 Watt, they investigated the long production networks of another sort of real, and yet imaginary, object as part of its production chain, producing a weird choreography of imaginary technology becoming a consumer product. Recently they embarked on a field trip to Congo, one that served both as artistic research and as a performance of returning some of the minerals back to the soil. The following text is a short excerpt from their travel diary: a meditation on a geography of the travels of minerals—the materials of media culture—as part of the postcolonial landscapes. From the microscopic dust returning to the soil, to the experience of gaining access to the mines, their images tell a backstory to the quiet colonial histories of media culture, now enhanced by the presence of global corporations from the ex-colonies and by newcomers from China. The images shown here are from their field trip and from art projects such as H/AlCuTaAu and D/AlCuNdAu. —Jussi Parikka

Cross-calibration of the Siemens mMR: easily acquired accurate PET phantom measurements, long-term stability and reproducibility.

BackgroundWe present a quick and easy method to perform quantitatively accurate PET scans of typical water-filled PET plastic shell phantoms on the Siemens Biograph mMR PET/MR system.We perform regular cross-calibrations (Xcal) of our PET systems, including the PET/MR, using a Siemens mCT water phantom.Long-term stabilityThe mMR calibration stability was evaluated over a 3-year period where 54 cross-calibrations were acquired, showing that the mMR on average underestimated the concentration by 16 %, consistently due to the use of MR-based μ-maps.The mMR produced the narrowest calibration ratio range with the lowest standard deviation, implying it is the most stable of the six systems in the study over a 3-year period.mMR accuracy with predefined μ-mapsWith the latest mMR software version, VB20P, it is possible to utilize predefined phantom μ-maps. We evaluated both the system-integrated, predefined μ-map of the long mMR water phantom and our own user-defined CT-based μ-map of the mCT water phantom, which is used for cross-calibration.For seven scans, which were reconstructed with correctly segmented μ-maps, the mMR produced cross-calibration ratios of 1.00–1.02, well within the acceptance range [0.95–1.05], showing high accuracy.ConclusionsThe mMR is the most stable PET system in this study, and the mean underestimation is no longer an issue with the easily accessible μ-map, which resulted in correct cross-calibration ratios in all seven tests. We will share the user-defined μ-map of the mCT phantom and the protocol with interested mMR users.

Theoretical and experimental analysis of elastic–plastic cylindrical shells under two types of axial impacts

In this paper, the dynamic buckling of axisymmetric circular cylindrical shells subjected to axial impact is investigated theoretically and experimentally. The von Mises yield criterion is used for the elastic–plastic cylindrical shell made of linear strain hardening material in order to derive the constitutive relations between stress and strain increments. Nonlinear dynamic circular cylindrical shell equations are solved with using finite difference method for two types of loading which are stationary cylindrical shells impacted axially and traveling cylindrical shells impacted against a rigid wall. Experimental tests for two types of loading are performed by gas gun. Theoretical and experimental results for cylindrical shells under axial impact for different loading conditions are reported and it is found that there is a good agreement between them.

Pavement Design Reinforced Base Researches

Stamp tests results of the two-layer basis from the crushed stone and sand reinforced by geogrid with steel fibers in a plastic shell are given in report. Deformation characteristics of the reinforced design are received. Experimentally established deflections of the reinforced basis are compared with the results received theoretically. Thus the reinforced layer of crushed stone is considered as a multilayered plate on the elastic basis. Bubnov-Galerkin's method of calculation is used. Satisfactory coincidence of theoretical and experimental results is received. The effect of reinforcement on deflections is established.

Hydrodynamic growth experiments with the 3-D, “native-roughness” modulations on NIF

Hydrodynamic instability growth experiments with threedimensional (3-D) surface-roughness modulations were performed on plastic (CH) shell spherical implosions at the National Ignition Facility (NIF). The initial capsule outer-surface roughness was similar to the standard specifications (“native roughness”) used in a majority of implosions on NIF. At a convergence ratio of ∼3, the measured tent modulations were close to those predicted by 3-D simulations (within ∼15-20%), while measured 3-D, broadband modulations were ∼3-4 times larger than those simulated based on the growth of the known imposed initial surface modulations. One of the hypotheses to explain the results is based on the increased instability amplitudes due to modulations of the oxygen content in the bulk of the capsule. These new experiments results have prompted looking for ways to reduce UV light exposure during target fabrication.

High-density implosion via suppression of Rayleigh–Taylor instability

Radiation hydrodynamic simulations of ICF capsules assuming a kJ-class laser facility were conducted to evaluate the hydrodynamic stability of a brominated plastic shell. An opacity table based on a detailed atomic model was employed so that more quantitative forecast of the implosion dynamics could be performed. A lightly doped shell could form a high-density core at the maximum compression by suppressing the hydrodynamic instability.

Experience in Improving the Manufacturing Properties of Semifinished Products and Quality of Thoriated Tungsten Products by the Deposition of Tungsten Coatings with WF6 Hydrogen Reduction

Tungsten deposition from a gaseous mixture of its hexafluoride with hydrogen on the surface of a porous billet of thoriated tungsten makes it possible to fasten the particles of peripheral layers and its core between each other, as well as to form a more plastic shell on the surface capable of relaxing stresses appearing during rotary forging, thus preventing the destruction of semifinished products. This procedure makes it possible to perform the rotary forging of a pilot batch of insufficiently sintered billets of thoriated tungsten, which would be destroyed if treated uncoated. The improvement of manufacturing properties can be used when fabricating similar tungsten-based compositions (of W(La2O3) and W(Y2O3)), as well as for other types of deformation. These results can be applicable for (i) lowering the sintering–welding temperature of bars (and rods) of dispersion-strengthened tungsten-based compositions, thereby reducing power consumption and increasing the overhaul period of equipment; (ii) increasing the sizes of semifinished products using the existing equipment thereby increasing the production process productivity and expanding the range of output products; (iii) producing less environmentally hazardous thoriated tungsten products, multiply reducing the radiation exposure of operators; and (iv) using composite cathodes in arc xenon lamps, thereby increasing their service life by a factor of 2–3.

Hydrodynamic growth and mix experiments at National Ignition Facility

Hydrodynamic growth and its effects on implosion performance and mix were studied at the National Ignition Facility (NIF). Spherical shells with pre-imposed 2D modulations were used to measure Rayleigh-Taylor (RT) instability growth in the acceleration phase of implosions using in-flight x-ray radiography. In addition, implosion performance and mix have been studied at peak compression using plastic shells filled with tritium gas and imbedding localized CD diagnostic layer in various locations in the ablator. Neutron yield and ion temperature of the DT fusion reactions were used as a measure of shell-gas mix, while neutron yield of the TT fusion reaction was used as a measure of implosion performance. The results have indicated that the low-mode hydrodynamic instabilities due to surface roughness were the primary culprits to yield degradation, with atomic ablator-gas mix playing a secondary role.

Development of a polar direct drive platform for mix and burn experiments on the National Ignition Facility

Capsules driven with polar drive [1, 2] on the National Ignition Facility [3] are being used [4] to study mix in convergent geometry. In preparation for experiments that will utilize deuterated plastic shells with a pure tritium fill, hydrogen-filled capsules with copper- doped deuterated layers have been imploded on NIF to provide spectroscopic and nuclear measurements of capsule performance. Experiments have shown that the mix region, when composed of shell material doped with about 1% copper (by atom), reaches temperatures of about 2 keV, while undoped mixed regions reach about 3 keV. Based on the yield from these implosions, we estimate the thickness of CD that mixed into the gas as between about 0.25 and 0.43 μm of the inner capsule surface, corresponding to about 5 to 9 μg of material. Using 5 atm of tritium as the fill gas should result in over 1013 DT neutrons being produced, which is sufficient for neutron imaging [5].

A simple reduced integration hexahedral solid-shell element for large strains

In this paper a hexahedral solid-shell element with in-plane reduced integration is developed. The element is intended to the analysis of thin/thick elastic–plastic shells with moderate to large strains. Developed within the framework of a total Lagrangian formulation, the element uses as strain measure the logarithm of the right stretch tensor (U) obtained from a modified right Cauchy–Green tensor (C̄). The modifications, in order to remove transverse shear, Poisson and volumetric locking, are three: (a) a classical assumed mixed shear strain approximation for C13 and C23 (b) an assumed strain approximation for the in-plane components Cαβ and (c) an enhanced assumed strain for the through the thickness normal component C33 (one additional degree of freedom). The first five components of C̄ are interpolated to the integration points from values at the center of the top and bottom faces. An arbitrary number of integration points is used in the transverse direction and a stabilization scheme is used to avoid spurious modes due to the in-plane sub integration. Several examples are presented that show the locking-free behavior and the very good performance of the presented element for the analysis of shells with geometric and material nonlinearities, including quasi-incompressible elastic and elastic–plastic with incompressible plastic flow models.

In vitro comparative evaluation of mechanical properties of temporary restorative materials used in fixed partial denture.

Introduction:Materials used to fabricate provisional restorations can be classified as acrylics or resin composites. Provisional crows can be either prefabricated or custom made.Acrylics:These materials have been used to fabricate provisional restorations since the 1930s and usually available as powder and liquid. They are the most commonly used materials today for both single-unit and multiple-unit restorations. In general, their popularity is due to their low cost, acceptable esthetics, and versatility.Composites:Composite provisional materials use bis-acryl resin, a hydrophobic material that is similar to bis-GMA. Composites are available as auto-polymerized, dualpolymerized and visible light polymerized.Preformed Crowns:Preformed provisional crowns or matrices usually consist of tooth-shaped shells of plastic, cellulose acetate or metal. They are commercially available in various tooth sizes and are usually selected for a particular tooth anatomy. They are commonly relined with acrylic resin to provide a more custom fit before cementation, but the plastic and metal crown shells can also be cemented directly onto prepared teeth.Aims and Objectives:The aim of this study is to choose a material to serve as a better interim prosthesis and to compare three different properties – flexural strength, compressive strength, and color stability.Materials and Methods:The samples were made with three different provisional materials (Revotek LC, Protemp 4, TemSpan).Result:It was inferred from the study that no one material was superior in all three tested parameters.

Large Displacements and the Stiffness of a Flexible Shell

The design of static thin shell structures can be carried out using analytical and numerical approaches. Recently, thin shells have been studied for their flexibility, which can be beneficial for adaptive systems. However flexible systems involve large displacements and precise kinematics. The analysis of flexible shell systems is challenging due to the nonlinearities induced by these large displacements. This study addresses the nonlinear behaviour and stress-stiffening effects caused by large displacements in a 0.80 m-long carbon fibre reinforced plastic shell consisting of two monolithically connected lobes. The structural behaviour of this system is investigated both numerically and experimentally. Following the analysis framework, the non-linear effects of the large displacements on the shell stiffness are numerically determined using eigenvalue analysis and the displacement response to external loading on deformed shell configurations. The numerical displacement results are compared with results obtained in the experimental study. In conclusion, our study shows that the stiffness of the shell system under study increases 113% during deformation. More precisely, we establish that this change in stiffness is governed by the presence of tensile stresses in the shell surface due to deployment rather than by the change of the system's geometry.

Identification of parameters of models of nonlinear deformation of isotropic and composite materials on the basis of calculations and experiments aimed at analyzing the dynamic behavior of cylindrical metal–plastic shells

A method for identification of material parameters of the constitutive relations of elastoplastic and viscoelastic deformation of isotropic and composite materials is developed. The method is based on minimizing the functional of the residue of results of numerical and experimental analysis of unsteady deformation of structural elements made of examined materials. The method is tested, and prospects of its application for determining material parameters of viscoelastic and elastoplastic models of nonlinear deformation of cylindrical metal–plastic shells under explosive loading are demonstrated.

E&amp;P Notes (November 2015)

E&amp;P Notes Digitizing Core Scans Brings Old Methods into 21st Century Trent Jacobs, JPT Senior Technology Writer In the search for oil and gas, one of the first investments that companies make is in the analysis of core samples. Pulled directly from the reservoir rock, core samples provide critical data used to determine how an exploration program should move forward, or if at all. However, compared with the high-tech methods found in so many other arenas of the oil and gas industry, the conventional methods used to examine core samples seem quite antiquated. Petroleum geologists are usually given the first look at the samples to measure key rock features such as natural fractures and to estimate the size of the rock grains. And among the tools most often used to make these measurements and provide a detailed description of the core are a magnifying hand lens, a ruler, and a pad of paper. As tried and true as these analog technologies have proven to be for much of the industry’s history, there is an ongoing transition to bring the process of core description into the digital age. Treating Damaged Subsea Lines With a Light Electrical Touch Stephen Rassenfoss, JPT Emerging Technology Senior Editor As subsea electric lines age, they are prone to cracks that allow seawater in, reducing their effectiveness, and if the leaks are bad enough, they can shut down operations. A British subsea engineering and equipment company is selling a novel repair option that can be installed without ever going into the water. Viper Subsea’s solution comes in the form of a box sending out specially programmed electrical signals. It has installed units on 17 umbilicals and subsea cables and it worked in all but two cases, said Max Nodder, business development director and cofounder of Viper, during a presentation at SPE Offshore Europe. For anyone whose mental image of insulation is a hard plastic shell isolating wires from the elements, Viper’s method may seem farfetched. But the conventional alternative is not easy to accept either, given the time and money required to replace subsea lines that can run for miles. Three Offshore Blocks Awarded in Mexico’s Second Auction Trent Jacobs, JPT Senior Technology Writer Mexico’s second oil and gas lease auction has been deemed a success after three out of five shallow-water blocks were awarded in September. The awarded areas contain an estimated 236 million bbl of oil and 190 Bcf of gas. The government expects the auction to result in a USD 3 billion investment and up to 90,000 B/D in production by the start of the next decade. The auction’s outcome was warmly welcomed by Mexico’s National Hydrocarbons Commission, known by its Spanish-language acronym CNH, which has been working for more than a year to organize the historic opening of the country’s exploration and production sector. “We believe that our mandate of obtaining the best conditions for the Mexican state was achieved,” said Edgar Rangel-German, a CNH commissioner. Halliburton Reveals Refracturing Strategy Trent Jacobs, JPT Senior Technology Writer Although refracturing is a topic that has gained a lot of interest, many shale producers have been sitting on the sidelines because early results did not justify the spending. Halliburton has now joined other service companies in announcing that its results prove the technology is ready for prime time. The company’s encouraging numbers show that on average, it is seeing ultimate recovery increases of 80% and a two-thirds reduction in the cost per incremental barrel of oil from a refractured well compared with each barrel from a new well. Priyesh Ranjan, a senior manager of global business development at Halliburton, presented the details of the company’s new Activate Refracturing Service in September. Speaking before an audience of oil and gas company representatives in Houston, Ranjan tried to dispel the notion that the majority of refracturing candidates are primarily vintage wells because of the improvements made in completion technologies and fracture designs in recent years. Middle East NOCs To Boost Collaboration in Joint Projects Abdelghani Henni, JPT Middle East Editor National oil companies (NOCs) in the Middle East plan to boost their collaboration efforts in technology applications through a global industry trade organization’s initiative. For the first time, Gulf Cooperation Council (GCC) members of the Industry Technology Facilitator (ITF) held a summit in Abu Dhabi. They agreed to take forward three technology challenges with the aim of defining a call for proposals for collaborative joint industry projects (JIPs) later this year. The summit was attended by representatives from the Abu Dhabi National Oil Company, Kuwait Oil Company, and Petroleum Development Oman, three of the six GCC members.

Study of the explosion characteristics and combustion products of air conditioner using flammable refrigerants

Due to ozone depletion and high global warming potential of chlorofluorocarbon, environmentally benign options such as hydrocarbons and hydrofluorocarbons (such as R290, R32) are under consideration. Since these refrigerants are flammable, they pose additional fire and explosion risks. The explosion pressures of R32 and R290 at different concentrations were studied using 20 L ball explosive test apparatus. The indoor unit combustion, total heat release, carbon monoxide, and carbon dioxide production were studied in the event of the indoor unit being ignited by an external fire. It is found that the maximum explosion pressures of R32 and R290 are basically the same. Besides, heat and smoke mainly come from the combustion of indoor unit plastic shell and compressor lubricants.

An extended shakedown theory on an elastic–plastic spherical shell

The article analyses one of possible optimization methodologies for ideal elastic–plastic structures at shakedown and its application for shallow spherical shells having prescribed geometry and affected by a variable repeated load (VRL) – a system of external forces that may vary independently of each other. The paper accepts that only time-independent upper and lower bounds of variations in external forces are given. The pronounced effect of external forces, i.e. in this context, possible histories of variations in forces, is not examined (the unloading phenomenon of cross-sections is ignored in the course of plastic deformation). The discussed concept of the structure at shakedown refers to the Melan theorem related to statically allowable admissible internal forces. Thus, for the discretization of the spherical shell, with the help of an assumption about small displacements, the equilibrium finite element method based on internal force approximation is applied. The limit axial force of the cross-section is supposed to be constant within the bounds of the finite element, and only the optimal distribution of limit internal forces among elements, according to the selected criterion, is in need of search. The article presents a discrete mathematical model for determining the optimal allocation problem with strength and stiffness requirements. The model conforms to the limit axial force of the shallow spherical shell of the variable repeated load and takes into account ultimate and serviceability limit states of EC3 with corresponding reliability levels. Structural optimization methods refer to extreme energy principles of mechanics and are illustrated with the numerical examples of spherical shell optimization.

Complete mitochondrial DNA sequences of Saccostrea mordax and Saccostrea cucullata: genome organization and phylogeny analysis

Classified in the phylum mollusks, oysters are bivalves which are found in estuaries and coastal zones. Because of their plastic shell, mitochondrial DNA analysis of this species becomes an interesting field, necessary to investigate their phylogenetic and evolution of relations. In our study, two oyster species: Saccostrea mordax and Saccostrea cucullata from Indian Ocean (Madagascar) were investigated. The complete sequence of Saccostrea mordax (16 512 bp) and Saccostrea cucullata (16 396 bp) were described and determined, with their mitogenomes deposited in the GenBank with accession number KP769562 and KP967577 respectively. Both mitochondrial genome sequences contained 12 protein-coding genes, 23 tRNAs, and two rRNAs, all encoded in the same heavy strand. High levels of similarity in the gene arrangement of the two Saccostrea species were evident. The phylogenetic analysis shows a closer relationship between the two Saccostrea species and confirms the strong relationship within Saccostrea, Crassostrea and Ostrea genus in taxonomy of Ostreidae family.