Perfect Symmetry Research Articles

Three-Dimensional Orofacial Changes Occurring After Proportional Condylectomy in Patients With Condylar Hyperplasia Type 1B (Unilateral Hemimandibular Elongation)

To evaluate 3-dimensional orofacial changes that occurred after proportional condylectomy that was not followed by orthognathic surgery in patients with condylar hyperplasia type 1B (unilateral hemimandibular elongation). This retrospective analysis used the medical records of 14 skeletally mature patients. Transverse, vertical, and horizontal cephalometric analyses of photographs and radiographs were undertaken. A comparison of preoperative and postoperative measurements was conducted. After proportional condylectomy, transverse chin position and vertical lip cant improved to various degrees, whereas ramus and condyle height and mandibular lower border discrepancy worsened to different extents. The prominence of the gonial angle of the affected (operated) side increased in all patients after surgery, and this contributed to better symmetry only when the preoperative prominence was small (flat), whereas the opposite occurred when the preoperative prominence was large (bulky). After condylectomy, there was posterior displacement of the pogonion point (setback), which was favorable in cases with a preoperative concave profile and unfavorable in cases with a preoperative convex profile. Proportional condylectomy can successfully arrest the hyperplastic growth of the affected condyle; however, it rarely achieves perfect symmetry of the face. Although it improves some facial features, other facial traits are worsened. Surgeons should have a full understanding of the 3-dimensional changes occurring after proportional condylectomy and should be able to predict, based on preoperative findings, the anticipated improvement or worsening of different facial features.

Scenario to chaos and multistability in a modified Coullet system: effects of broken symmetry

Recently, the study of nonlinear systems with multiple attractors has drained the attention of researchers worldwide owing to its fundamental and technological relevance. In this work, we consider a modified Coullet system with a cubic polynomial nonlinearity in the form $$ \varphi_{m} \left( x \right) = x - mx^{2} - x^{3} $$ where $$ m $$ is a control parameter. The new system bridges the gap between chaotic systems with symmetry and those without symmetry. In fact for $$ m = 0 $$ , the system displays a perfect symmetry which is reflected on the location of equilibria, the type of attractors, and the shape of basins of attraction as well. In this special case, multistability involves a pair of mutually symmetric periodic or chaotic attractors, a pair of chaotic attractors with a pair of limit cycles, two pairs of limit cycles with a pair of chaotic attractors, and so on. For $$ m \ne 0 $$ , the system is non symmetric and more complex nonlinear phenomena are observed such as parallel bifurcation branches, coexisting multiple asymmetric attractors, and hysteresis. For instance, the coexistence of a stable fixed point with a limit cycle, two different non symmetric limit cycles or chaotic attractors, three or four different non symmetric periodic and chaotic attractors are reported when monitoring the system parameters and initial conditions as well. Basins of attraction with non-trivial basin boundaries structures are computed to visualize the magnetization of the state space in the presence of multiple attractors. Experimental results based on a suitable electronic implementation of the proposed jerk system are included.

Emergent electrochemistry in spin ice: Debye-Hückel theory and beyond

The low-temperature picture of dipolar spin ice in terms of the Coulomb fluid of its fractionalised magnetic monopole excitations has allowed analytic and conceptual progress far beyond its original microscopic spin description. Here we develop its thermodynamic treatment as a `magnetolyte', a fluid of singly and doubly charged monopoles, an analogue of the electrochemical system ${\rm 2 H_2O = H_3O^+ +OH^- = H_4O^{2+} + O^{2-}}$, but with perfect symmetry between oppositely charged ions. For this lattice magnetolyte, we present an analysis based on Debye-H\"uckel theory, which is accurate at all temperatures and incorporates `Dirac strings' imposed by the microscopic ice rule constraints at the level of Pauling's approximation. Our results are in close agreement with the specific heat from numerical simulations as well as new experimental measurements with an improved lattice correction, which we present here, on the spin ice materials $\mathrm{Ho_2Ti_2O_7}$ and $\mathrm{Dy_2Ti_2O_7}$. Our study of the magnetolyte shows how electrochemistry can emerge in non-electrical systems. We also provide new experimental tests of Debye-H\"uckel theory and its extensions. The application of our results also yields insights into the electrochemical behaviour of water ice and liquid water, which are closely related to the spin ice magnetolyte.

Mapping, invivo, the uniformity of two skin properties alongside the human face by a 3D virtual approach.

To determine the homogeneity in the distribution of two cutaneous functions (hydration and elasticity) along the entire human face. The half faces (right or left, randomly chosen) of two groups of Caucasian women were measured on 24 different small sites (elasticity) and 41 others (hydration), by instruments of small-sized probes (Cutometer® and Corneometer® , respectively). Hydration of the face was recorded at different times (up to 24h), post application of a highly hydrating product. The recorded values (left and right half faces) were further gathered and digitally positioned on a virtual feminine face and their intensity was illustrated through a colored white (lower values)-blue (higher values) scale. The reconstitution of the mapping of the two measured parameters (from the left and right sides of different subjects), shows a perfect symmetry vis à vis the nose axis. However, both parameters present slightly variable but significant values along the human face. Sites from the temple are less elastic than chin or forehead. The upper and lower parts of the forehead show slight disparities in their elasticity values. Cheeks are significantly less prone at retaining their imparted hydration status (lost 2h after application of a hydrating product) as compared to sub-ocular regions or chin that retain their hydration up to 24h. Attempts to establish a mutual relationship between the two skin properties unsurprisingly failed. The two studied skin properties show a slight but highly symmetric disparity along the entire human face.

Human body symmetry and immune efficacy in healthy adults

More symmetric organisms are perceived as more attractive. Fluctuating asymmetry (FA) i.e. small, random deviations from perfect bilateral symmetry, is supposed to inform about developmental instability. According to the good genes hypothesis, a low level of FA is a putative cue to an organism's biological quality. An important aspect of this quality is the immune system functioning. The aim of this study was to evaluate the relationship between immune system functioning and body symmetry in healthy people. The composite body FA (cFA) was assessed on the basis of six bilateral traits (on hands and feet). The ISF was determined by many innate (total complement and lysozyme activity, neutrophils function) and adaptive immune parameters (T CD3 and B CD19 lymphocytes, total IgA and IgG and response to flu vaccine). A total of 98 men and 92 women were subjected to flu (among them 37 men and 30 women also to tetanus) vaccination. The blood samples were collected before and 4 weeks after the antigens exposure. Immunomodulatory factors: participant's age, body fat, and free testosterone level, were controlled. Apart from the weak positive association between CD3 or CD19 and cFA in men, we found no association between the level of body symmetry and the rest of the analyzed immune parameters for both sexes. Our results are the opposite of the good genes hypothesis prediction and suggest that in western, healthy populations, human mate preferences for more symmetric bodies are not related to immune competence.

Morphometric Analyses of (Hidden) Directional Asymmetry in Leaf Blades

The deviation from perfect bilateral symmetry is a phenomenon actively exploring in evolutionary and environmental studies. The bilateral variation presents on different ecosystem level. The methods applied vary depending on the task and the final goal of study. The present study demonstrates the statistically significant presence of components (traces) of directional asymmetry (DA), fluctuating asymmetry (FA) and antisymmetry (AS) in leaf blade of Betula pendula on low level of ecosystem such as tree and leaf blade. The Generalized Procrustes Analysis was applied for testing asymmetry of shape in all data set and subgroups. The category ‘population’ revealed no significant value of DA (factor ‘side’). In the levels ‘tree’ and ‘leaf blade’ the factor ‘side’ was statistically significant as well as fluctuating asymmetry (factor interaction ‘leaf × side’).The principal component analysis showed visually the difference in PC scores between antisymmetry matrices of the left and right halves of the leaf blade. Covariate analysis matrices demonstrated the shape deviation from strict symmetry. The metric traits showed directional asymmetry in t-test in the leaf blade and the low kurtosis values. Permutation test of kurtosis values in geometric morphometric approach showed deviation from normality that could verified as a weak presence AS traces. The discriminant analysis results showed that traces of DA differed at the subpopulation level, as three of 10 populations revealed not significant factor ‘side’. Descriptive statistics of the metric train showed a correspondence to the trace of directional asymmetry in the shape of leaf blade. Fluctuating asymmetry in its pure form, at three levels of ecosystem was met only in single population of ten that should be taken into account testing developmental stability of birch and possibly other woody plants.

Elbow Kinematics During Gait Improve With Age in Children With Hemiplegic Cerebral Palsy.

Children with hemiplegic cerebral palsy (hCP) exhibit a typical posture of elbow flexion during gait. However, the change in elbow kinematics and symmetry during gait across age span in both hCP and typically developing (TD) children is not well described. The aim of this study was to quantify the change in elbow kinematics and symmetry across age span in hCP children compared with TD children. Upper extremity kinematic data were extracted and analyzed from a database for gait studies performed between 2009 and 2015. A total of 35 hCP and 51 TD children between the ages of 4 and 18 (mean age: TD=11.2±0.6, hCP=9.8±0.5) met inclusionary criteria. The groups were further subdivided into 3 age categories: 4 to 7, 8 to 11, 12+ years old. Elbow angles were extracted and peak elbow flexion, overall range of motion during gait, and asymmetry indices were calculated. A 1-way analysis of variance was performed on each group with post hoc Tukey honestly significant difference pairwise comparisons. Peak elbow flexion during gait increased with age in TD children (P<0.05) and decreased with age in hCP children on the affected side (P<0.05). There was no change on the less affected side of hCP children. TD children demonstrated significantly less elbow flexion (mean=51.9±2.1 deg.) compared with the affected side in hCP (mean=82.1±3.8 deg.) across all age categories (P<0.05). There was no change in elbow asymmetry index (0=perfect symmetry) across age in either controls or hCP children; however, there were differences between hCP and TD groups in younger age groups (TD=28, hCP=62, P<0.05) that resolved by adolescence (TD=32, hCP=40). During gait, hCP children have greater peak elbow flexion on the affected side than do TD children. Peak elbow flexion angle converged between the 2 groups with age, decreasing in hCP children and increasing in TD children. Furthermore, elbow symmetry during gait improves with age in hCP children, approximating symmetry of TD children by adolescence. These findings have implications for both consideration and optimal timing of surgical intervention to improve elbow flexion in children with hCP. Level III-retrospective case-control study.

Waking From the Dream: The Arcades Project, Copia , and the American Consumer

Waking From the DreamThe Arcades Project, Copia, and the American Consumer Laura Morowitz (bio) When the project really started getting legs I started thinking about this idea in reference to the turn of the century, from the nineteenth to the twentieth, how there were some really interesting parallels, especially in visual culture and art, I was specifically thinking about the Post-Impressionists and Manet and Gustave Caillebotte, the great painting at the Art Institute of Chicago. It's kind of weird how in a sense that was almost like what we would call street photography, looking at culture and trying to see this psychological undertone and cultural underpinnings, similar, except the only difference was instead of walking down the Parisian boulevards or sitting at the train station it was now Walmart. —Brian Ulrich, Art Uncovered, November 2011 For while the relation of the present to the past is a purely temporal, continuous one, the relation of what-has-been to the now is dialectic: is not progression but image, suddenly emergent. — Walter Benjamin, The Arcades Project (N2, A3) In Brian Ulrich's photograph Cleveland, Ohio, 2003 (fig. 1), from his series Copia (2001–2011), a little girl in a red coat turns her back on the overstuffed shelves and perfect symmetry of a Disney Store display, bewildered by the scene. Behind her, in faded purple, rises Cinderella's castle, the site of twenty-first-century childhood fantasy. With her bright jacket and soft face, she has begun to resemble the cuddly toys behind her.1 While the stuffed tigers seem to laugh at a joke in which we may be the punch line, Eeyore casts a decidedly concerned glance in the little girl's direction, as if she might be on the brink of danger. [End Page 1] Click for larger view View full resolution Figure 1. Brian Ulrich, Cleveland, Ohio, 2003, from Copia: Retail, color photograph. Collection: Ulrich. The image captures perfectly both the lure of consumer culture and its threat to engulf us in fantasy. No corporation has been more successful than Disney in trafficking in our collective dreams. Centuries of humanity's legacy—the European fairy tale—are largely accessed now through the entertainment industry and its commodities. Its products hold power over us in part because they reach back to our deepest instincts and collective unconscious; benevolent kingdoms and harmonious villages are accessible now not through oral transmission but through computer games and packaged videos. In addition to its exploration of the bright gleam and highly ordered spaces of the box stores and malls of the United States, Copia equally images the worn and discarded products that overflow the shelves of thrift and secondhand stores and the shuttered malls that dot the American landscape since the economic downturn of 2008 (fig. 2). The perfect symmetry and vivid colors that characterize the earlier images become chaotic and faded, while the structures themselves remain only as ghosts of themselves. [End Page 2] Click for larger view View full resolution Figure 2. Brian Ulrich, Pep Boys 3, 2009, from Copia: Dark Stores, color photograph. Collection: Ulrich. The photographic oeuvre of Brian Ulrich has been widely and ingeniously analyzed; his record of modern consumer culture has been mined for its poetic resonance and the way it lays bare the inner workings of contemporary American life.2 Despite their powerful evocation of twenty-first-century consumption, the photographs that constitute Copia are haunted by ideas and images first articulated by the German philosopher and critic Walter Benjamin, in his magisterial—and never finished—The Arcades Project of the 1930s. It's a paradox: Benjamin's The Arcades Project, written by a twentieth-century German to elucidate nineteenth-century Paris, being used here to illuminate twenty-first-century America. Benjamin himself might have savored such a set of historical displacements. In the following pages, I argue that a close reading of Benjamin's texts unlocks some of the mythic, phantasmagoric content of Ulrich's images and that the photographs, in their specificity, give form to Benjamin's doomed project and to his concept of the dialectical image. In this essay, I use the language and imagery of The Arcades Project to...

Resonant metasurface with tunable asymmetric reflection

Suppression of backscattered electromagnetic waves by carefully designed structures is highly demanded in a range of applications, some of which are radar invisibility, antenna isolation, and many others. Salisbury screens, composed of a mirror with an additional layer on top, are traditionally used for these purposes. Here, we report on the design and experimental demonstration of a reciprocal screen, which demonstrates asymmetric reflection properties when illuminated from opposite directions. The structure utilizes near-field magneto-electric coupling between subwavelength split ring resonators and wires, forming a metasurface. While the reciprocal structure demonstrates perfect symmetry in transmission, strong backscattered asymmetry is shown to be controllable by carefully choosing the Ohmic losses, which are implemented with lumped resistors soldered into the resonators. Depending on the load, the meta-screen demonstrates switching properties that vary between fully symmetric and completely asymmetric reflection between the forward and backward directions of incident illumination. The frequency selective surface acts as a Huygens element when illuminated from one side and as a perfect mirror when illuminated from the other. The ability to tailor the asymmetric reflectance of electromagnetic metasurfaces by controlling Ohmic losses allows employing additional degrees of freedom in designing of radomes and other antenna devices. Furthermore, the concept could be extended to optical frequencies, where resistive losses can be controlled via direct carrier injection into semiconductor devices.

Bioengineering Strategies for Protein-Based Nanoparticles.

In recent years, the practical application of protein-based nanoparticles (PNPs) has expanded rapidly into areas like drug delivery, vaccine development, and biocatalysis. PNPs possess unique features that make them attractive as potential platforms for a variety of nanobiotechnological applications. They self-assemble from multiple protein subunits into hollow monodisperse structures; they are highly stable, biocompatible, and biodegradable; and their external components and encapsulation properties can be readily manipulated by chemical or genetic strategies. Moreover, their complex and perfect symmetry have motivated researchers to mimic their properties in order to create de novo protein assemblies. This review focuses on recent advances in the bioengineering and bioconjugation of PNPs and the implementation of synthetic biology concepts to exploit and enhance PNP’s intrinsic properties and to impart them with novel functionalities.

Role of nanosize icosahedral quasicrystal of Mg-Al and Mg-Ca alloys in avoiding crystallization of liquid Mg: Ab initio molecular dynamics study

We have used highly accurate first-principles molecular dynamics simulations to explore the structural (both topological and chemical ordering) evolution during solidification of Mg90Ca10 and Mg90Al10 liquids upon cooling. Using various structural analysis methods, we find that local atomic structure of both amorphous alloys are characterized by major distorted and perfect icosahedral symmetry. The fraction of fivefold icosahedra around Mg atoms in Mg-Ca alloy is higher than in Mg-Al alloy. Eutectic Mg90Ca10 alloy shows strong chemical short range order, which further increases upon cooling. In contrast, Mg90Al10 shows weak chemical short range ordering which seems to show weak temperature dependency behavior. The fraction of fivefold icosahedral symmetry, which is responsible for geometrical frustration, and the atomic size are responsible for the dynamic slowdown and causing glassy formation.

Towards More Realistic Leaf Shapes in Functional-Structural Plant Models

Fluctuating asymmetry in plant leaves is a widely used measure in geometric morphometrics for assessing random deviations from perfect symmetry. In this study, we considered the concept of fluctuating asymmetry to improve the prototype leaf shape of the functional-structural plant model L-Cucumber. The overall objective was to provide a realistic geometric representation of the leaves for the light sensitive plant reactions in the virtual plant model. Based on three-dimensional data from several hundred in situ digitized cucumber leaves comparisons of model leaves and measurements were conducted. Robust Bayesian comparison of groups was used to assess statistical differences between leaf halves while respecting fluctuating asymmetries. Results indicated almost no directional asymmetry in leaves comparing different distances from the prototype while detecting systematic deviations shared by both halves. This information was successfully included in an improved leaf prototype and implemented in the virtual plant model L-Cucumber. Comparative virtual plant simulations revealed a slight improvement in plant internode development against experimental data using the novel leaf shape. Further studies can now focus on analyses of stress on the 3D-deformation of the leaf and the development of a dynamic leaf shape model.

Circular data in biology: advice for effectively implementing statistical procedures

Circular data are common in biological studies. The most fundamental question that can be asked of a sample of circular data is whether it suggests that the underlying population is uniformly distributed around the circle, or whether it is concentrated around at least one preferred direction (e.g. a migratory goal or activity phase). We compared the statistical power of five commonly used tests (the Rayleigh test, the V-test, Watson’s test, Kuiper’s test and Rao’s spacing test) across a range of different unimodal scenarios. The V-test showed higher power for symmetrical distributions, Rao’s spacing performed worst for all explored unimodal distributions tested and the remaining three tests showed very similar performance. However, the V-test only applies if the hypothesis is restricted to one (pre-specified) direction of interest. In all other unimodal cases, we recommend using the Rayleigh test. Much less explored is the multimodal case with data concentrated around several directions. We performed power simulations for a variety of multimodal situations, testing the performance of the widely used Rayleigh, Rao’s, Watson, and Kuiper’s tests as well as the more recent Bogdan and Hermans-Rasson tests. Our analyses of alternative statistical methods show that the commonly used tests lack statistical power in many of multimodal cases. Transformation of the raw data (e.g. doubling the angles) can overcome some of the issues, but only in the case of perfect f-fold symmetry. However, the Hermans-Rasson method, which is not yet implemented in any software package, outcompetes the alternative tests (often by substantial margins) in most of the multimodal situations explored. We recommend the wider uptake of the powerful but hitherto neglected Hermans-Rasson method. In summary, we provide guidance for biologists helping them to make decisions when testing circular data for single or multiple departures from uniformity.

Fluctuating asymmetry in the shell shape of the Atlantic Patagonian mussel, Mytilus platensis, generated by habitat-specific constraints

Fluctuating asymmetry (FA) consists of random deviations from perfect symmetry, and it is a useful trait to monitor developmental stability and ecological stress. The principal goal in this work was to study shell shape FA in Mytilus platensis as a measure of stress of living in intertidal wild areas compared to subtidal cultured ones. Shell shape asymmetry was studied by geometric morphometrics using landmarks and semilandmarks from internal and external anatomical structures. We analyzed FA comparing shell shape from 452 individuals living at different habitats (intertidal rocky shores vs. subtidal longlines) in two Patagonian sites. We predict that mussels living in the intertidal present higher levels of morphological alterations (i.e., FA) than those from the subtidal, where the environmental stress is lower. We based the asymmetry analysis on the FA scores from Procrustes ANOVA; all effects of the model were statistically significant. The Procrustes FA scores differed significantly between habitats: intertidal populations presented higher FA scores than subtidal ones. As predicted, shell shape in Mytilus platensis is influenced by the habitat and these differences add evidence to the fact that FA is a suitable measure of developmental instability, indicating the inability of species to buffer stress in its developmental pathways.

A new cochliodont anterior tooth plate from the Mississippian of Alabama (USA) having implications for the origin of tooth plates from tooth files

BackgroundPaleozoic holocephalian tooth plates are rarely found articulated in their original positions. When they are found isolated, it is difficult to associate the small, anterior tooth plates with the larger, more posterior ones. Tooth plates are presumed to have evolved from fusion of tooth files. However, there is little fossil evidence for this hypothesis.ResultsWe report a tooth plate having nearly perfect bilateral symmetry from the Mississippian (Chesterian Stage) Bangor Limestone of Franklin County, Alabama, USA. The high degree of symmetry suggests that it may have occupied a symphyseal or parasymphyseal position. The tooth plate resembles Deltodopsis? bialveatus St. John and Worthen, 1883, but differs in having a sharp ridge with multiple cusps arranged along the occlusal surface of the presumed labiolingual axis, rather than a relatively smooth occlusal surface. The multicusped shape is suggestive of a fused tooth file. The middle to latest Chesterian (Serpukhovian) age is determined by conodonts found in the same bed.ConclusionThe new tooth plate is interpreted as an anterior tooth plate of a chondrichthyan fish. It is referred to Arcuodus multicuspidatus Itano and Lambert, gen. et sp. nov. Deltodopsis? bialveatus is also referred to Arcuodus.

A general printing approach for scalable growth of perovskite single-crystal films.

Perovskite single-crystal films, which exhibit exceptionally low trap density and nearly perfect translational symmetry, are believed to achieve the highest performance of perovskite-based optoelectronic devices. However, fabrication of these perovskite single-crystal films is quite difficult because of the uncontrollable nucleation caused by the rapid reaction of two perovskite precursors. We report a facile seed printing approach to selectively create millimeter-sized perovskite single-crystal films with controlled thickness and high yield. We show that perovskite single-crystal films can be perfectly transferred to almost arbitrary substrates through the printing process. The as-grown perovskite single-crystal films have excellent crystalline quality and morphology. We further demonstrate that perovskite single-crystal films can be directly printed for scalable fabrication of photodetectors and effective image sensors. This strategy allows high-yield fabrication of large perovskite single-crystal films for functional devices and may extend to other solution-processed materials for wide applications.

Contrasting Modes of Self-Assembly and Hydrogen-Bonding Heterogeneity in Chlorosomes of Chlorobaculum tepidum.

Chlorosome antennae form an interesting class of materials for studying the role of structural motifs and dynamics in nonadiabatic energy transfer. They perform robust and highly quantum-efficient transfer of excitonic energy while allowing for compositional variation and completely lacking the usual regulatory proteins. Here, we first cast the geometrical analysis for ideal tubular scaffolding models into a formal framework, to relate effective helical properties of the assembly structures to established characterization data for various types of chlorosomes. This analysis shows that helicity is uniquely defined for chlorosomes composed of bacteriochlorophyll (BChl) d and that three chiral angles are consistent with the nuclear magnetic resonance (NMR) and electron microscope data for BChl c, including two novel ones that are at variance with current interpretations of optical data based on perfect cylindrical symmetry. We use this information as a starting point for investigating dynamic and static heterogeneity at the molecular level by unconstrained molecular dynamics. We first identify a rotational degree of freedom, along the Mg–OH coordination bond, that alternates along the syn–anti stacks and underlies the (flexible) curvature on a larger scale. Because rotation directly relates to the formation or breaking of interstack hydrogen bonds of the O–H···O=C structural motif along the syn–anti stacks, we analyzed the relative fractions of hydrogen-bonded and the nonbonded regions, forming stripe domains in otherwise spectroscopically homogeneous curved slabs. The ratios 7:3 for BChl c and 9:1 for BChl d for the two distinct structural components agree well with the signal intensities determined by NMR. In addition, rotation with curvature-independent formation of stripe domains offers a viable explanation for the localization and dispersion of exciton states over two fractions, as observed in single chlorosome fluorescence decay studies.

Facile Synthesis of Monodisperse Silver Nanospheres in Aqueous Solution via Seed-Mediated Growth Coupled with Oxidative Etching.

Because of their perfect geometrical symmetry, spherical metal nanoparticles have attracted much attention for various applications, including fundamental studies and construction of plasmonic devices. In this work, monodisperse silver nanospheres (Ag NSs) in aqueous solution were directly prepared by a continuous process of seed-mediated growth followed by oxidative etching. Silver nanocubes (Ag NCs) were synthesized by a seed-mediated growth method and subsequently were transformed to Ag NSs by simple injection of Cu2+ to the freshly prepared Ag NCs solution. Not requiring any centrifugation steps at both growth and etching stages makes this procedure convenient and efficient. The etching process and morphology evolution of silver nanostructure were monitored by UV-vis spectromater, SEM, and XRD. Monodisperse Ag NSs with broadly tunable diameters (from 37 to 68 nm) have been successfully prepared. The optical property of Ag NSs has been studied and the experimental results show fairly good consistency with simulation results. Furthermore, these Ag NSs prepared by our approach could be constructed into ordered superlattice by self-assembly technique based on their high monodispersity and sphericity.

A novel superconducting magnetic levitation method to support the laser fusion capsule by using permanent magnets

A novel magnetic levitation support method is proposed, which can relieve the perturbation caused by traditional support methods and provide more accurate position control of the capsule. This method can keep the perfect symmetry of the octahedral spherical hohlraum and has the characteristics in stability, tunability and simplicity. It is also favorable that all the results, such as supporting forces acting on the superconducting capsule, are calculated analytically, and numerical simulations are performed to verify these results. A typical realistic design is proposed and discussed in detail. The superconducting coating material is suggested, and the required superconducting properties are listed. Damped oscillation of the floating capsule in thin helium gas is discussed, and the restoring time is estimated.

Maximizing Ionic Mobility By Lattice Disorder in Anti-Perovskite Solid Electrolytes

Amongst these requirements for Li-ion batteries, ensuring safe operation is near the top of the list. Liquid electrolytes, widely used in commercial Li-ion batteries, have safety issues due to their volatility and flammability. Also, they may suffer from dendrite formation which can yield an internal short-circuit. In principle, solid electrolytes avoid these problems and furthermore open the possibility of using a metallic Li anode that highly increases the energy density. Recently, the anti-perovskites Li3OCl was suggested as one of promising solid electrolytes due to its high ionic conductivity.1 The correlation between high ionic conductivity and disorder has been discussed previously. Here, disorder can refer to an amorphous phase,2 disorder in the occupation of a sub-lattice,3 or in the rotational degrees of freedom of complex anions.4 The anti-perovskite system presents an ideal venue to further explore the connection between ionic mobility and disorder, in terms of the tolerance factor5 that describes the degree of disorder. The disorder can systematically be introduced by substitutions of chalcogen and halogen ions. Then, the system will lose the perfect cubic symmetry in the forms of octahedral tilting and distortion.5 In this study, anti-perovskite solid electrolytes M3XY (M = Li or Na, X = O, S, or Se and Y = F, Cl, Br or I) are thoroughly examined to compare barrier energies of pathways and investigate the correlation between lattice disorder and high ionic mobility. The density functional theory (DFT) was used to predict atomic structures and minimum energy pathways. The lattice deviates from perfect cubic symmetry as octahedral disorder is induced by substitutions of anions, and the degree of disorder increases with higher variation of tolerance factor. We calculated barrier energies of all possible individual migration paths for vacancies and interstitial ions, and found minimum energy pathway that can contribute to the macroscopic ionic transport. We reveal a clear correlation between high ionic conductivity and the lattice disorder. Compounds with higher disorder exhibits lower barriers for the migration of vacancies and interstitials, thus the disorder plays a key role in reducing the huddle for ionic migration. Therefore, it suggests that tuning lattice structure in terms of disorder can maximize the ionic conductivity. Perfect cubic symmetry presents only one unique ionic migration path along twelve octahedron edges, whereas the disorder causes environmental differences between paths due to the broken symmetry. It leads to the segregation of individual paths into energetically favorable and unfavorable channels for ionic migration. Compounds with higher degree of disorder show wider segregation and lower barriers of favorable paths. Therefore, higher disorder provides the possibility to create migration pathways by combining individual paths with low barriers and achieve high ionic conductivity.