Increasing Shell Thickness Research Articles

Evaluation of PSMA-PET Biology-Guided Radiotherapy Sequential Boost to the PSMA-avid Subvolume in the Prostate Region in Low-Volume Advanced Prostate Cancer

Biology-guided radiation therapy (BgRT) is a new technology that aims to deliver radiation based on detecting positron emissions in real time. BgRT combined with prostate specific membrane antigen (PSMA) PET/CT imaging may be an attractive option for prostate cancer patients with low-volume pelvic nodes and distant metastases since all lesions may be treated during the same session. This study investigates the feasibility of BgRT sequential boost to the PSMA-avid subvolume (PAS) in the prostate region. The ratio of standard uptake value (SUV) to background SUV is quantified, with specific focus on adjacent bladder uptake.Patients enrolled in the ProPSMA prospective single-institution clinical trial underwent Ga-68-PSMA-11 PET scan at the time of prostate cancer diagnosis. Those with pelvic node or distant metastases were selected for analysis. PAS gross target volume (GTV) was delineated on the PET component of a PET/CT acquisition by using a PET edge tool in commercially available software. Three dimensional shells of thickness 5 mm, 10 mm and 20 mm were created by expanding the GTV to characterize the uptake background and to determine suitability of BgRT based on these tracking zones. Normalized SUV (nSUV) was calculated as the ratio of SUVmax in the GTV to SUVmean of the adjacent shell. Lesions with nSUV larger than 3 were defined to be suitable for BgRT. An increase in nSUV with increasing shell thickness indicates absence of uptake surrounding the GTV.From the ProPSMA patient cohort of 89 patients, 24 patients had at least one pelvic nodal or distant metastases. PAS GTV volume ranged from 1 cc to 147 cc (median = 25 cc, IQR = 12 cc - 62 cc). GTV SUVmax varied from 6.4 to 80 (median = 21.5; IQR = 14 - 33). nSUV ranged from 3.4 to 21.2 (median = 6.4; IQR = 4.9 - 8.5), from 4.1 to 20.9 (median = 8.6; IQR = 6 - 10.5), and from 2.8 to 31.4 (median = 8.2; IQR = 5.4 - 13.8) in 5 mm, 10 mm, and 20 mm shell, respectively. Moreover, 100%, 100%, and 96% of lesions had nSUV greater than 3 in a shell thickness of 5 mm, 10 mm, and 20 mm, respectively. nSUV increased from the 5 mm shell to the 10 mm shell in 75% of patients and from the 10 mm shell to the 20 mm in 46% patients, indicating the absence of bladder uptake.An nSUV greater than 3 was achieved in more than 95% of all GTVs for all shell thicknesses investigated in this study, which suggests that PSMA-guided BgRT is a feasible modality for sequential boost directed at the dPSMA-avid subvolume in the prostate region. If bladder proximity impacts geometric specificity of BgRT delivery or if greater tumor-to-background contrast is desired, additional refinements may be required. These may include modifications to the BgRT algorithm that enable masking of the bladder. Clinical trial number ACTRN12617000005358.

Explosion Hazard of AP/HTPB in Fire Condition

ABSTRACT To study the thermal stability of solid propellant, a temperature model of pool fire is built to replace the uniform temperature rise model in previous studies. The model can better show the effect of different fire stages on solid propellant. Based on the AP/HTPB cook-off model, an effective method to evaluate the thermal safety of propellants is proposed by changing the heating distance and shell thickness. The thermal explosion process of AP/HTPB in fire conditions is numerically simulated, and the ignition temperature and ignition delay time are predicted. The results show that the ignition delay time increases and the ignition temperature decreases with the extension of heating distance. When the distance exceeds 500 mm, the ignition delay time increases rapidly and the ignition temperature remains stable at about 560 K. The shell thickness has an obvious effect on the ignition delay time, but has little effect on ignition temperature. The ignition delay time increases by 25% for each 2 mm increase in shell thickness. The simulation results fit the experimental data well, which provides a reliable reference for the assessment of the explosion hazard of AP/HTPB in fire conditions.

Thermal and mechanical stabilities of Core-shell microparticles containing a liquid core

Thorough understanding of the behaviour of core–shell microparticles with a liquid core is essential for determining their performance in applications under different operation conditions. This paper reports the behaviour of core–shell particles with a liquid core under thermal and mechanical loads. First, we formulated an analytical model for the heating process of a core–shell microparticle with a liquid core. Next, we utilised an axisymmetric model of an elastic spherical shell upon compression to describe the deformation of a core–shell microparticle. Finally, we conducted experiments to validate these models. Both thermal and mechanical models agree well with the experimental data. The maximum temperature a core–shell microparticle can withstand depends on the liquid, the geometry, and the material of the shell. The critical compression force before rupture of a core–shell microparticle depends on the Poisson’s ratio of the shell material and the shell thickness relative to the outer shell radius. The rupture force and rupture temperature increase with increasing shell thickness.

Templated Mesoporous Silica Outer Shell for Controlled Silver Release of a Magnetically Recoverable and Reusable Nanocomposite for Water Disinfection.

In this work, we encapsulated Fe3O4@SiO2@Ag (MS-Ag), a bifunctional magnetic silver core-shell structure, with an outer mesoporous silica (mS) shell to form an Fe3O4@SiO2@Ag@mSiO2 (MS-Ag-mS) nanocomposite using a cationic CTAB (cetyltrimethylammonium bromide) micelle templating strategy. The mS shell acts as protection to slow down the oxidation and detachment of the AgNPs and incorporates channels to control the release of antimicrobial Ag+ ions. Results of TEM, STEM, HRSEM, EDS, BET, and FTIR showed the successful formation of the mS shells on MS-Ag aggregates 50-400 nm in size with highly uniform pores ∼4 nm in diameter that were separated by silica walls ∼2 nm thick. Additionally, the mS shell thickness was tuned to demonstrate controlled Ag+ release; an increase in shell thickness resulted in an increased path length required for Ag+ ions to travel out of the shell, reducing MS-Ag-mS' ability to inhibit E. coli growth as illustrated by the inhibition zone results. Through a shaking test, the MS-Ag-mS nanocomposite was shown to eradicate 99.99+% of a suspension of E. coli at 1 × 106 CFU/mL with a silver release of less than 0.1 ppb, well under the EPA recommendation of 0.1 ppm. This high biocidal efficiency with minimal silver leach is ascribed to the nanocomposite's mS shell surface characteristics, including having hydroxyl groups and possessing a high degree of structural periodicity at the nanoscale or "smoothness" that encourages association with bacteria and retains high Ag+ concentration on its surface and in its close proximity. Furthermore, the nanocomposite demonstrated consistent antimicrobial performance and silver release levels over multiple repeated uses (after being recovered magnetically because of the oxidation-resistant silica-coated magnetic Fe3O4 core). It also proved effective at killing all microbes from Long Island Sound surface water. The described MS-Ag-mS nanocomposite is highly synergistic, easy to prepare, and readily recoverable and reusable and offers structural tunability affecting the bioavailability of Ag+, making it excellent for water disinfection that will find wide applications.

Evaluation of 3D-printer settings for producing personal protective equipment.

Aim: COVID-19 resulted in a shortage of personal protective equipment. Community members united to 3D-print face shield headbands to support local healthcare workers. This study examined factors altering print time and strength. Materials & methods: Combinations of infill density (50%, 100%), shell thickness (0.8, 1.2 mm), line width (0.2 mm, 0.4 mm), and layer height (0.1 mm, 0.2 mm) were evaluated through tensile testing, finite element analysis, and printing time. Results: Strength increased with increased infill (p < 0.001) and shell thickness (p < 0.001). Layer height had no effect on strength. Increasing line width increased strength (p < 0.001). Discussion: Increasing layer height and line width decreased print time by 50 and 39%, respectively. Increased shell thickness did not alter print time. These changes are recommended for printing.

Synthesis of Chemically Stable Ultrathin SiO2-Coated Core-Shell Perovskite QDs via Modulation of Ligand Binding Energy for All-Solution-Processed Light-Emitting Diodes.

Recently, perovskite quantum dots (QDs) have attracted intensive interest due to their outstanding optical properties, but their extremely poor chemical stability hinders the development of the high-performance perovskite QD-based light-emitting diodes (PeLEDs). In this study, chemically stable SiO2-coated core-shell perovskite QDs are prepared to fabricate all-solution-processed PeLEDs. When the SiO2 shell thickness increases, the chemical stability of perovskite QDs is dramatically improved, while the charge injection efficiency is significantly decreased, which becomes the biggest obstacle for PeLED applications. Thus, controlling the SiO2 thickness is essential to obtain core-shell perovskite QDs optimal for PeLEDs in an aspect of chemical and optoelectrical properties. The 3-aminopropyl-triethoxysilane (APTES)/oleylamine (OAm) volume ratio is found to be a critical factor for obtaining an ultrathin SiO2 shell. Optimization of the APTES/OAm ratio affords A-site-doped CsPbBr3 QDs with an ultrathin SiO2 shell (A-CsPbBr3@SiO2 QDs) that exhibit longer radiative lifetimes and smaller shallow trap fraction than those without A-site doping, resulting in a higher photoluminescence quantum yield. A-CsPbBr3@SiO2 QDs also demonstrate long-term superior chemical stability in polar solvents without loss of optical properties due to passivation by the SiO2 shell and less defects via A-site doping. Consequently, all-solution-processed PeLED is successfully fabricated under ambient conditions, facilitating perovskite QD utilization in low-cost, large-area, flexible next-generation displays.

Numerical simulation of radiated noise during combustion of energetic materials in a closed bomb

In this study, based on a closed bomb test combined with computational fluid dynamics, a structural finite element method, and an acoustic boundary element method, a fluid-solid acoustic one-way coupling calculation model is established for the combustion process of energetic materials in a closed bomb, and the effectiveness of the model is verified by experiments. It is found that the maximum peak sound pressure increases exponentially with an increase in loading doses or gas pressure. However, a change in the combustion coefficient of the energetic materials has little effect on the noise generated during the combustion process in the closed bomb. When the combustion coefficient is reduced by a multiple of 16, the maximum transient sound pressure is reduced by 1.79 dB, and the sound pressure level in the frequency band is reduced by 1.75 dB. With an increase in shell thickness, the combustion noise of the energetic materials in the closed bomb decreases, and the reduction range of the combustion noise increases with the increase in shell thickness.

Long‐term increases in shell thickness in Elliptio complanata (Bivalvia: Unionidae) in the freshwater tidal Hudson River

Abstract The shells of freshwater molluscs are highly plastic in response to environmental and ecological conditions, which can affect ecological interactions and ecosystem functioning. We tested for changes in relative shell thickness in the unionid bivalve Elliptio complanata in the freshwater tidal Hudson River over 1991–2017, a period of changing water chemistry and predation pressure. Shells of both juveniles (shells &lt;20 mm long) and larger animals became substantially (c. 10%–25%) and significantly heavier (for a given shell length) over the study period. This parallels previously published results for the non‐native zebra mussel Dreissena polymorpha in the Hudson. Increased shell thickness during the study period could be explained by rising pH, alkalinity, and temperature, which increased calcite saturation and favoured the precipitation of calcium carbonate shells, as well as a response to greater predation by shell‐crushing predators. Because the factors that affect shell thickness (e.g. calcium carbonate saturation and presence and abundance of predators) are changing rapidly in many lakes and rivers, similar large changes in shell thickness may be occurring in fresh waters around the world, affecting ecological interactions and ecosystem functioning.

A Detailed Investigation of the Onion Structure of Exchanged Coupled Magnetic Fe3-δO4@CoFe2O4@Fe3-δO4 Nanoparticles.

Nanoparticles that combine several magnetic phases offer wide perspectives for cutting edge applications because of the high modularity of their magnetic properties. Besides the addition of the magnetic characteristics intrinsic to each phase, the interface that results from core-shell and, further, from onion structures leads to synergistic properties such as magnetic exchange coupling. Such a phenomenon is of high interest to overcome the superparamagnetic limit of iron oxide nanoparticles which hampers potential applications such as data storage or sensors. In this manuscript, we report on the design of nanoparticles with an onion-like structure which has been scarcely reported yet. These nanoparticles consist of a Fe3-δO4 core covered by a first shell of CoFe2O4 and a second shell of Fe3-δO4, e.g., a Fe3-δO4@CoFe2O4@Fe3-δO4 onion-like structure. They were synthesized through a multistep seed-mediated growth approach which consists consists in performing three successive thermal decomposition of metal complexes in a high-boiling-point solvent (about 300 °C). Although TEM micrographs clearly show the growth of each shell from the iron oxide core, core sizes and shell thicknesses markedly differ from what is suggested by the size increasing. We investigated very precisely the structure of nanoparticles in performing high resolution (scanning) TEM imaging and geometrical phase analysis (GPA). The chemical composition and spatial distribution of atoms were studied by electron energy loss spectroscopy (EELS) mapping and spectroscopy. The chemical environment and oxidation state of cations were investigated by 57Fe Mössbauer spectrometry, soft X-ray absorption spectroscopy (XAS) and X-ray magnetic circular dichroism (XMCD). The combination of these techniques allowed us to estimate the increase of Fe2+ content in the iron oxide core of the core@shell structure and the increase of the cobalt ferrite shell thickness in the core@shell@shell one, whereas the iron oxide shell appears to be much thinner than expected. Thus, the modification of the chemical composition as well as the size of the Fe3-δO4 core and the thickness of the cobalt ferrite shell have a high impact on the magnetic properties. Furthermore, the growth of the iron oxide shell also markedly modifies the magnetic properties of the core-shell nanoparticles, thus demonstrating the high potential of onion-like nanoparticles to accurately tune the magnetic properties of nanoparticles according to the desired applications.

Nonlinear optical behavior of Au@Ag core- shell nanostructures

Core-shell structure has been getting tremendous research interest due to their tunable multifunctional properties, induced as a result of the co-occurrence of more than one nanostructured phases. Here we report detailed nonlinear optical studies of Au@Ag core-shell nanostructures under ns pulse excitation. The size and shell thickness of the core-shells were obtained from TEM images. A significant blue shift from 519 nm to 411 nm in surface plasmon maxima is observed on forming Ag (shell) layer on Au (core) nanosphere and a slight red shift (411 nm to 425 nm) was observed as the shell thickness increases from 7.5 to 22.5 nm. All the samples exhibited reverse saturable absorption behavior and the extent of optical limiting activity enhanced on increasing the shell thickness. Nonlinear refraction properties of the samples were also analyzed and all the samples were found to be exhibiting negative nonlinearity. Improved optical limiting activity on increasing shell thickness of the studied system could be attributed to enhanced local field effect and nonlinear scattering effect, which is confirmed from the finite difference time domain simulation analysis. The good nonlinear optical properties of Au@Ag core-shell structures ensure its potential for future nonlinear optical applications.

A non-classical model for circular cylindrical thin shells incorporating microstructure and surface energy effects

A non-classical model for circular cylindrical thin shells is developed by using a modified couple stress theory and a surface elasticity theory. The equations of motion and boundary conditions are simultaneously obtained by a variational formulation based on Hamilton’s principle, which provides a unified treatment of the microstructure and surface energy effects. The new non-classical shell model contains one material length scale parameter to capture the microstructure effect and three surface elastic constants to describe the surface energy effect. The current model includes the shell models considering the microstructure effect only or the surface energy effect alone as special cases. Also, the newly developed shell model reduces to the classical circular cylindrical Love–Kirchhoff thin shell model when both the microstructure and surface energy effects are suppressed. In addition, it recovers the non-classical model for Kirchhoff plates incorporating the microstructure and surface energy effects when the shell radius tends to infinity. To illustrate the new model, the static bending and free vibration problems of a simply supported closed circular cylindrical shell and of an open circular cylindrical shell with free edge boundary conditions are analytically solved by directly applying the model. For the static bending problem in each case, the numerical results show that the shell deflection predicted by the current model is smaller than that predicted by the classical model, and the difference is significant when the shell is very thin but diminishes as the shell thickness increases. For the free vibration problem in each case, it is found that the natural frequency predicted by the new model is higher than that predicted by its classical counterpart, and the difference is large only for very thin shells.

Regulating dielectric performances of Poly(vinylidene fluoride) nanocomposites by individually controlling shell thickness of Core@Double‐Shells structured nanowires

The synthesis of core@double-shells structured TiO2@C@SiO2 nanowires (NWs) with variable thickness of carbon inner shell and SiO2 outer shell was achieved by individually controlling the chemical vapour deposition time and amount of silicon precursor added in the sol–gel synthesis. The resultant TiO2@C@SiO2 NWs filled nanocomposites exhibited an excellent dielectric performance with simultaneously improved dielectric constant and suppressed dielectric loss, which could be further regulated by individually controlling the carbon inner shell and SiO2 outer shell thickness. More importantly, the influences of the conductive carbon inner shell and insulated SiO2 outer shell thickness on the dielectric performance of nanocomposites were clearly revealed. The increase of the conductive carbon inner shell thickness would lead to an increase in dielectric constant and loss of nanocomposites, while the insulated SiO2 outer shell exhibited a totally opposite law that the dielectric constant and loss of nanocomposites decrease with increasing SiO2 outer shell thickness. Numerical simulations were also carried out to theoretically verify the relationship between the dielectric loss and SiO2 outer shell thickness. This promising controllable multi-shell structure could be extended to a variety of hybrids to develop high-performance dielectric nanocomposites.

Exciton and Bi-exciton Binding Energy Calculation in a Core Shell Quantum Dot

We report the effect of shell thickness on exciton and biexciton binding energy calculation for a CdSe/ZnSe core shell quantum dot. Wentzel Kramers Brillouin approximation help us to create proper wave function for the system. It incorporates core shell boundary effect correctly. For excitons, the binding energy is affected by the Columbic confinement potentials and during biexciton binding energy calculation, the exchange and correlation effects were taken into account. It is observed that the excitonic binding energy shows an initial increase with increasing shell thickness but saturates for thick shell while it always gives a negative value for bi-excitonic binding energy. This confirms the existence of antibonding states for biexcitons.

Controllable chiral behavior of type-II core/shell quantum dots adjusted by shell thickness and coordinated ligands.

Chiral semiconductor nanomaterials induced by capped chiral ligands are of great interest for both theoretical studies and advanced applications. In this study, CdTe/CdSe quantum dots (QDs), defined as type-II core/shell nanostructure, with the advantage of a good separation of holes and electrons are imparted chirality with L/D-cysteine and L/D-penicillamine molecules. Circular dichroism (CD) at exciton transitions from cysteine- and penicillamine-capped QDs is different in shape and intensity. CD intensities decrease with increasing shell thickness from three monolayers to six monolayers, indicating a decreased hybridization degree between the holes in CdTe core and the electrons in chiral ligands. Elevated cysteine concentration leads to decreased g-factor, probably due to an altered binding mode from tridentate to bidentate. Our observations provide further insights into the understanding of chiral phenomenon as well as optimized design and applications of chiral nanostructures.

A non-classical model for first-ordershear deformation circular cylindrical thin shells incorporating microstructure and surface energy effects

A new non-classical model for first-order shear deformation circular cylindrical thin shells is developed by using a modified couple stress theory and a surface elasticity theory. Through a variational formulation based on Hamilton’s principle, the equations of motion and boundary conditions are simultaneously obtained, and the microstructure and surface energy effects are treated in a unified manner. The newly developed non-classical shell model contains one material length-scale parameter to account for the microstructure effect and three surface elastic constants to capture the surface energy effect. The new model includes shell models considering the microstructure effect only or the surface energy effect alone as special cases and recovers the first-order shear deformation circular cylindrical thin shell model based on classical elasticity as a limiting case. In addition, the current shell model reduces to the non-classical model for Mindlin plates incorporating the microstructure and surface energy effects when the thin shell radius tends to infinity. To illustrate the new model, the static bending and free vibration problems of a simply supported circular cylindrical thin shell are analytically solved. The numerical results reveal that the inclusion of the microstructure and surface energy effects leads to reduced shell deflections and rotation angles and increased natural frequencies. The differences are significant when the shell is very thin, but they diminish as the shell thickness increases. These predicted size effects at the micron scale agree with the general trends observed in experiments.

Production performance and egg quality in Kuzi ducks of Odisha

Production performances and egg quality parameters of Kuzi ducks of Odisha were studied in 40 drakes and 240 duck sinintensive system of rearing under hot and humid climate conditions. The body weight recorded at first egg of the flock was 1568±3.76g in ducks and 1730±43.45g in drakes. First egg of the flock was obtained at 110.67±3.76 days and age at 50% duck house egg production was 135.33±5.60 days. Age of the flock at peak (90%) duck house egg production was 167.67±6.06 days. Duck day egg production calculated at 4 weeks interval revealed that there is no definite trend however, as the age advances there was a decrease in egg production % after 60 weeks of age. The egg weight increased with the ages and the egg weight at 40 weeks of age was 64.26±0.48g. The egg production of the duck up to 40 weeks of age was 110.79±4.42 eggs and up to 72 weeks of age were 217.68±4.96 eggs. Significant differences inegg weight, shape index, albumen index, yolk colour, shell thickness and Haugh unit score were observed at different weeks of age. Further, as the age of the bird advances there was decrease in Haugh unit and albumen index with increase in egg shell thickness. The internal quality decreased with increase in age of the bird. The production performance showed that the Kuzi ducks may be used as an egg type ducks.

Fine‐Tuning Au@Pd Nanocrystals for Maximum Plasmon‐Enhanced Catalysis

AbstractCore–shell nanocrystals with plasmonic metals as cores and catalytic metals as shells, have recently received considerable attention due to their enhanced catalytic properties under visible light irradiation. However, it remains illusive how sizes/shapes of cores and shells influence catalytic efficiency. Here, using Au@Pd nanocrystals as a model system, key parameters including Au core size/shape and Pd shell thickness are scrutinized to systematically examine how they influence reaction rate. The comparison is based on normalizing Pd amount, which is important from economics standpoint. The results show that the reaction rate decreases with the increase in shell thickness. With the fixed shell thickness, the maximum reaction rate occurs in the smallest core. Among four different core shapes (nanocube, nanorod, nanohexagon, and nanostar), Au@Pd nanorods display the highest reaction rate and the highest plasmonic enhancement factor. These findings may provide a rational route to screen desired plasmonic nanocatalyst with a balanced consideration of efficiency and economics.

Thickness control of TiN network in CoCrFeNi matrix composite with tunable microstructure

A bottom up approach is designed where a TiN coated CoCrFeNi core- core-shell powder was used as a building block to fabricate CoCrFeNi matrix composites with tunable microstructure. Initially, the core-shell powder was achieved by surface nitriding of mechanically alloyed CoCrFeNiTi powder. By controlling the treatment parameters, powders with variable shell thickness were achieved. Afterwards, the core-shell powder was sintered via spark plasma sintering. The sintered microstructures consisted of CoCrFeNi matrix along with a continuous network of TiN. After sintering of for powders with a thin shell, the matrix phase was Ti rich resulting in the precipitation of intermetallic phase. Additionally, the reinforcement network showed high connectivity. As the shell thickness was increased, the matrix became Ti deficient resulting in the suppression of intermetallic precipitation. The increase in shell thickness also caused discontinuities in the reinforcement network. These microstructural changes impacted the thermal and mechanical properties of the resultant composite. The reinforcement network significantly reduced the coefficient of thermal expansion of the matrix phase. Additionally, all composites showed fracture strength in excess of 1 GPa showing excellent reinforcement efficiency in the designed microstructure.

The Effects of a Varied Gold Shell Thickness on Iron Oxide Nanoparticle Cores in Magnetic Manipulation, T1 and T2 MRI Contrasting, and Magnetic Hyperthermia.

Fe3O4–Au core–shell magnetic-plasmonic nanoparticles are expected to combine both magnetic and light responsivity into a single nanosystem, facilitating combined optical and magnetic-based nanotheranostic (therapeutic and diagnostic) applications, for example, photothermal therapy in conjunction with magnetic resonance imaging (MRI) imaging. To date, the effects of a plasmonic gold shell on an iron oxide nanoparticle core in magnetic-based applications remains largely unexplored. For this study, we quantified the efficacy of magnetic iron oxide cores with various gold shell thicknesses in a number of popular magnetic-based nanotheranostic applications; these included magnetic sorting and targeting (quantifying magnetic manipulability and magnetophoresis), MRI contrasting (quantifying benchtop nuclear magnetic resonance (NMR)-based T1 and T2 relaxivity), and magnetic hyperthermia therapy (quantifying alternating magnetic-field heating). We observed a general decrease in magnetic response and efficacy with an increase of the gold shell thickness, and herein we discuss possible reasons for this reduction. The magnetophoresis speed of iron oxide nanoparticles coated with the thickest gold shell tested here (ca. 42 nm) was only ca. 1% of the non-coated bare magnetic nanoparticle, demonstrating reduced magnetic manipulability. The T1 relaxivity, r1, of the thick gold-shelled magnetic particle was ca. 22% of the purely magnetic counterpart, whereas the T2 relaxivity, r2, was 42%, indicating a reduced MRI contrasting. Lastly, the magnetic hyperthermia heating efficiency (intrinsic loss power parameter) was reduced to ca. 14% for the thickest gold shell. For all applications, the efficiency decayed exponentially with increased gold shell thickness; therefore, if the primary application of the nanostructure is magnetic-based, this work suggests that it is preferable to use a thinner gold shell or higher levels of stimuli to compensate for losses associated with the addition of the gold shell. Moreover, as thinner gold shells have better magnetic properties, have previously demonstrated superior optical properties, and are more economical than thick gold shells, it can be said that “less is more”.

Critical buckling load analysis on spherical shells under various geometric imperfections

The strength of shell structures is mainly determined by their ability to resist buckling. However, the presence of geometric imperfections – a condition which the geometry is no longer the same as the original condition – significantly deteriorates the critical load and often leads to catastrophic failure. Ratio between the actual critical buckling load to the theoretical prediction is called knockdown factor. The study aims to analyse the critical buckling load on spherical dome elastic shells under various geometric imperfections. This study was conducted into several thicknesses (10, 16, 20, 37, 50 mm) and fixed base radius of 4000 mm. Analyses of linear buckling and nonlinear static are performed and aided with finite element program using MIDAS FEA. The result of this study reveals that the critical buckling load decreases sharply in the beginning of imperfection, then reach for quite slow progression until a constant value of Kd = 0.1. In addition, the higher minimum knockdown factor is obtained as the shell thickness increases.