Reshaping Process Research Articles

Multi-domain simulations of shock wave interaction with aerodynamic obstacles in cylindrical implosions

A multi-domain finite-volume approach is presented to simulate the interaction of converging shock waves and aerodynamic obstacles for dilute gases. The so-called reshaping process, in which the cylindrical shock is reshaped into a polygonal shock due to the presence of obstacles along the shock path, is studied. To accurately capture the diverse spatial scales of the problem, the computational domain is divided into three sub-domains, namely, the far-field region, the obstacle region and the focus region. Shock propagation in the far-field region is simulated under the axisymmetric, namely, one-dimensional approximation. The obstacle region is described by a fully two-dimensional model, in which initial conditions are interpolated from the far-field. The solution in the obstacle region is then interpolated into the focus region surrounding the center of the imploding shock. These two regions partially overlap to allow for linear interpolation. Numerical results are presented for air in dilute conditions and for four, eight, sixteen and twenty four aerodynamic obstacles. The proposed multi-domain solution technique is found to be capable of describing the complex gas dynamics of the shock propagation and reshaping, while reducing the computational burden for a large number of obstacles of one order of magnitude with respect to fully two-dimensional simulations.

“This has more to do with who I am than with my skills” – Student teacher subjectification in Finnish teacher education

This article addresses the argument that in order to offer responsive teacher education which acknowledges student teachers as active members in their education process, teacher educators need to know more about who student teachers are. The context of the research is Finland, in which teacher education is highly selective. The interest in this article is on the process of shaping and re-shaping of student teacher-selves in response to the surrounding implicit norms – a process of student teacher subjectification. Using purposefully constructed narrative data and thematic analysis we identified how students negotiate the implicit social and cultural expectations towards teachers.

Ex vivo culture of Drosophila pupal testis and single male germ-line cysts: dissection, imaging, and pharmacological treatment.

During spermatogenesis in mammals and in Drosophila melanogaster, male germ cells develop in a series of essential developmental processes. This includes differentiation from a stem cell population, mitotic amplification, and meiosis. In addition, post-meiotic germ cells undergo a dramatic morphological reshaping process as well as a global epigenetic reconfiguration of the germ line chromatin—the histone-to-protamine switch.Studying the role of a protein in post-meiotic spermatogenesis using mutagenesis or other genetic tools is often impeded by essential embryonic, pre-meiotic, or meiotic functions of the protein under investigation. The post-meiotic phenotype of a mutant of such a protein could be obscured through an earlier developmental block, or the interpretation of the phenotype could be complicated. The model organism Drosophila melanogaster offers a bypass to this problem: intact testes and even cysts of germ cells dissected from early pupae are able to develop ex vivo in culture medium. Making use of such cultures allows microscopic imaging of living germ cells in testes and of germ-line cysts. Importantly, the cultivated testes and germ cells also become accessible to pharmacological inhibitors, thereby permitting manipulation of enzymatic functions during spermatogenesis, including post-meiotic stages.The protocol presented describes how to dissect and cultivate pupal testes and germ-line cysts. Information on the development of pupal testes and culture conditions are provided alongside microscope imaging data of live testes and germ-line cysts in culture. We also describe a pharmacological assay to study post-meiotic spermatogenesis, exemplified by an assay targeting the histone-to-protamine switch using the histone acetyltransferase inhibitor anacardic acid. In principle, this cultivation method could be adapted to address many other research questions in pre- and post-meiotic spermatogenesis.

<em>Ex vivo</em> Culture of <em>Drosophila</em> Pupal Testis and Single Male Germ-line Cysts: Dissection, Imaging, and Pharmacological Treatment

During spermatogenesis in mammals and in Drosophila melanogaster, male germ cells develop in a series of essential developmental processes. This includes differentiation from a stem cell population, mitotic amplification, and meiosis. In addition, post-meiotic germ cells undergo a dramatic morphological reshaping process as well as a global epigenetic reconfiguration of the germ line chromatin—the histone-to-protamine switch. Studying the role of a protein in post-meiotic spermatogenesis using mutagenesis or other genetic tools is often impeded by essential embryonic, pre-meiotic, or meiotic functions of the protein under investigation. The post-meiotic phenotype of a mutant of such a protein could be obscured through an earlier developmental block, or the interpretation of the phenotype could be complicated. The model organism Drosophila melanogaster offers a bypass to this problem: intact testes and even cysts of germ cells dissected from early pupae are able to develop ex vivo in culture medium. Making use of such cultures allows microscopic imaging of living germ cells in testes and of germ-line cysts. Importantly, the cultivated testes and germ cells also become accessible to pharmacological inhibitors, thereby permitting manipulation of enzymatic functions during spermatogenesis, including post-meiotic stages. The protocol presented describes how to dissect and cultivate pupal testes and germ-line cysts. Information on the development of pupal testes and culture conditions are provided alongside microscope imaging data of live testes and germ-line cysts in culture. We also describe a pharmacological assay to study post-meiotic spermatogenesis, exemplified by an assay targeting the histone-to-protamine switch using the histone acetyltransferase inhibitor anacardic acid. In principle, this cultivation method could be adapted to address many other research questions in pre- and post-meiotic spermatogenesis.

The appropriation of the concept of intertextuality for translation-theoretic purposes

The present article offers a critical account of key applications of the concept of intertextuality for translation-theoretic purposes. It is argued that these applications form part of a reorientation in Western translation studies that involves a significant reconceptualization of both the practice of translation and the role of the translator. Seen from this perspective, the translation-theoretic appropriation of the concept of intertextuality presents itself as a particular moment of a reshaping process in the development of the discipline. The translation-theoretic import of the concept in question is examined against the backdrop of precisely this reshaping process.

Corneal Power Change Is Predictive of Myopia Progression in Orthokeratology

This study aims to investigate the relationship between corneal refractive power change along three axes (nasal, temporal, and inferior) after orthokeratology (OK) treatment and 2-year axial growth in children. Thirty-two Chinese children aged from 9 to 14 were fitted with OK. When corneal reshaping process following OK treatment was completed and stabilized, the 3-month topographic outputs were taken as the post-OK data. Corneal refractive powers along the nasal, temporal, and inferior axes were collected over an 8-mm-diameter ring in 1-mm steps using the sagittal power map. The maximum power change along each axis was selected and divided into two subcategories, level 1 and level 2, depending on whether the value was below or above the average. Axial length (AL) was measured every 6 months during a 24-month period. The relationship between the maximum power changes and 2-year axial elongation were analyzed. Twenty-seven subjects completed the 24-month study. After OK treatment, statistically significant steepening (p < 0.05) was observed at the nasal 2 mm and 3 mm; temporal 3 mm; and inferior 2 mm, 3 mm, and 4 mm locations compared with the apical center. AL increased significantly throughout the 24-month observation period (p < 0.001). Changes in corneal refractive power significantly affected axial elongation (nasal, p = 0.001; temporal, p = 0.011; inferior, p = 0.001). Two-year axial elongation in patients with larger corneal power changes (level 2) was reduced by 54% to 69% compared with those with smaller corneal power changes (level 1). Maximum power changes along the three axes were negatively correlated (p < 0.05) with 2-year axial growth. Subjects with larger magnitude of corneal relative peripheral power change along specific axes after OK treatment experienced slower axial elongation by the end of 24 months. This effect might be mediated by the induction of greater amount of relative myopic defocus on the peripheral retina. Our study lends weight to potential OK lens designs for myopia control in children.

Vein action: Performativity and the material body in haemodialysis

For patients suffering from acute kidney failure technology is the only means of survival until a kidney graft can be secured1 - a process which may take several years. In this article I focus on patients’ ongoing, situated, and embodied practices of knowing and doing as part of their caring for kidney failure. In these practices the action of blood, veins, needles, and the dialysis machine are of central import. I argue that kidney failure is »done« through a variety of cultural practices, including medical technology. It is a process of material re-shaping I term ‘vein action’. The concept of "doing" is elaborated upon by linking it to theories of neo-materialism and particularly Karen Barad’s notion of intra-activity. I investigate how flowing of blood between the patient and the dialysis machine is constituted by analyzing the material and performative qualities of these entities as part of living with kidney failure. I ask how does the materiality of the body, needle, and machine affect the doing of dialysis, and by extension the doing of kidney failure, in an everyday context? What does doing dialysis tell us about the nature of care-oriented agency?

CO2-Stimulated Diversiform Deformations of Polymer Assemblies

Use of a given physiological stimulus to delicately deform polymer assemblies is a challenging topic. Here we develop synthetic block copolymers to construct a series of CO2-sensitive self-assembled nanostructures that can simulate controllable deformations of the organelles in different ways. By controlling the CO2 stimulation levels, one can modulate the size, shape, and morphology of the polymer aggregates, which is conducive to understanding the stimuli-triggered dynamic reshaping process of polymer assemblies in aqueous solution.

Generation of parabolic similaritons in tapered silicon photonic wires: comparison of pulse dynamics at telecom and mid-infrared wavelengths

We study the generation of parabolic self-similar optical pulses in tapered Si photonic nanowires (Si-PhNWs) at both telecom (λ=1.55 μm) and mid-infrared (λ=2.2 μm) wavelengths. Our computational study is based on a rigorous theoretical model, which fully describes the influence of linear and nonlinear optical effects on pulse propagation in Si-PhNWs with arbitrarily varying width. Numerical simulations demonstrate that, in the normal dispersion regime, optical pulses evolve naturally into parabolic pulses upon propagation in millimeter-long tapered Si-PhNWs, with the efficiency of this pulse-reshaping process being strongly dependent on the spectral and pulse parameter regime in which the device operates, as well as the particular shape of the Si-PhNWs.

Energy shedding during nonlinear self-focusing of optical beams

Self-focusing of intense laser beams and pulses of light in real nonlinear media is in general accompanied by material losses that require corrections to the conservative Nonlinear Schrödinger equations describing their propagation. Here we examine loss mechanisms that exist even in lossless media and are caused by shedding of energy away from the self-trapping beam making it to relax to an exact solution of lower energy. Using the conservative NLS equations with absorbing boundary conditions we show that energy shedding not only occurs during the initial reshaping process but also during oscillatory propagation induced by saturation of the nonlinear effect. For pulsed input we also show that, depending on the sign and magnitude of dispersion, pulse splitting, energy shedding, collapse or stable self-focusing may result.

Pathological Neural Attractor Dynamics in Slowly Growing Gliomas Supports an Optimal Time Frame for White Matter Plasticity

Neurological function in patients with slowly growing brain tumors can be preserved even after extensive tumor resection. However, the global process of cortical reshaping and cerebral redistribution cannot be understood without taking into account the white matter tracts. The aim of this study was to predict the functional consequences of tumor-induced white matter damage by computer simulation. A computational model was proposed, incorporating two cortical patches and the white matter connections of the uncinate fasciculus. Tumor-induced structural changes were modeled such that different aspects of the connectivity were altered, mimicking the biological heterogeneity of gliomas. The network performance was quantified by comparing memory pattern recall and the plastic compensatory capacity of the network was analyzed. The model predicts an optimal level of synaptic conductance boost that compensates for tumor-induced connectivity loss. Tumor density appears to change the optimal plasticity regime, but tumor size does not. Compensatory conductance values that are too high lead to performance loss in the network and eventually to epileptic activity. Tumors of different configurations show differences in memory recall performance with slightly lower plasticity values for dense tumors compared to more diffuse tumors. Simulation results also suggest an optimal noise level that is capable of increasing the recall performance in tumor-induced white matter damage. In conclusion, the model presented here is able to capture the influence of different tumor-related parameters on memory pattern recall decline and provides a new way to study the functional consequences of white matter invasion by slowly growing brain tumors.

AUTOMATIC OBJECT DETECTION AND SEGMENTATION OF THE HISTOCYTOLOGY IMAGES USING RESHAPABLE AGENTS

The aim of this study is to suggest a method for automatic detection and segmentation of the target objects in the microscopic histology/cytology images. The detection is carried out by rectangular shapes then segmentation process starts utilizing flexible agents which are able to move and change their shapes according to a cost function. The agents are rectangular at the beginning then they gradually fit to the corresponding objects using a stochastic reshaping algorithm. The iterative reshaping process is controlled by a cost function and it is resulted in a finer segmentation of the target objects. The cost functional of the proposed method comprised of three terms including the prior shape, regional texture and gradient information. The experiments were carried out using a publicly available microscopy image dataset which contains 510 manually-labeled target cells. The segmentation performance of the proposed method is compared with another state of the art segmentation method. The results demonstrate satisfactory detection and segmentation performance of the proposed method.

Adaptive beam reshaping in Kerr optical media with a thermally induced nonlocality

Heat load on material surfaces can induce an abrupt change in their optical responses, leading to novel transmission properties which can be quite advantageous from both experimental and technological standpoints. The process of beam reshaping induced by thermal lensing is considered for an optical medium with a self-focusing nonlinearity, the refractive index of which possesses an extra nonlocal component caused by thermo-optic effects. By solving simultaneously the heat equation and the nonlinear propagation equation for an anisotropic material, a rich variety of double-pulse beam patterns is found. It emerges that the polarization, intensities, widths and phases of individual pulses in the double-pulse structures can be tailored by adjusting the characteristic parameters of the thermal nonlocal potential.

High resolution transmission electron microscopy in situ investigation into the spontaneous coalescence of gold nanoparticles at room temperature

The coalescence process of two gold nanoparticles was observed in situ by High Resolution Transmission Electron Microscopy (HRTEM). The observations reveal that the gold nanoparticles coalesced into one at room temperature. The HRTEM images show the relative rotation of the gold nanoparticles in order to align their crystal orientations for the attachment, which is the critical step of the coalescence and followed by the diffusion-mediated reshaping process.

Effect of hole shapes on the reliability of deeply‐etched InP‐based photonic crystal devices

AbstractWe present systematic evaluation of the optical transmission characteristics of a set of photonic crystal waveguides (PhCWs) fabricated by two schemes. An optimized hole‐reshaping process to obtain cylindrical holes was applied in one scheme and a comparison is made with as‐etched PhCWs. The spectral characteristics of the transmission mini‐ stopband (MSB) in identical waveguides show that the reliability, in terms of spectral position and shape, of fabricated PhCWs using the hole reshaping process is significantly improved in comparison to the as‐etched waveguides. The obtained MSB characteristics are attractive for coarse WDM filtering and wavelength selective mirrors. (© 2012 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

Direct phase and amplitude characterization of femtosecond laser pulses undergoing filamentation in air

Measurement of the temporal (spectral) phase and amplitude of a 50 fs laser pulse approaching and exceeding the critical power for self-focusing (P(crit)) in air reveals the formation of an isolated 17 fs pulse at 3P(crit). The dynamics of self-shortening are measured directly in the filament using transient-grating cross-correlation frequency-resolved optical gating with a noble gas serving as the nonlinear medium. Our results support recent filamentary propagation simulations, suggesting that a Kerr-dominated temporal reshaping process toward the end of the filament is largely responsible for the generation of short pulses.

Synthesizing style-preserving cartoons via non-negative style factorization

We present a complete framework for synthesizing style-preserving 2D cartoons by learning from traditional Chinese cartoons. In contrast to reusing-based approaches which rely on rearranging or retrieving existing cartoon sequences, we aim to generate stylized cartoons with the idea of style factorization. Specifically, starting with 2D skeleton features of cartoon characters extracted by an improved rotoscoping system, we present a non-negative style factorization (NNSF) algorithm to obtain style basis and weights and simultaneously preserve class separability. Thus, factorized style basis can be combined with heterogeneous weights to re-synthesize style-preserving features, and then these features are used as the driving source in the character reshaping process via our proposed subkey-driving strategy. Extensive experiments and examples demonstrate the effectiveness of the proposed framework.

DEM simulation of rotation-induced reshaping and disruption of rubble-pile asteroids

A Soft-Sphere Discrete Element Method (SSDEM) is used to simulate the rotational reshaping and disruption of cohesionless self-gravitating granular aggregates (as a representation of “rubble-pile” asteroids). Aggregates with spherical and ellipsoidal shapes are subjected to impulsive increments of their angular velocity to initiate a reshaping process leading up to the disruption of the aggregate. Internal stress fields are monitored during the process as well as critical angular velocities to initiate reshaping. In addition, the time evolution of other parameters such as filling fraction, angle of friction, mechanical energy, yield stress, semi-axes, density and mass dependence are also analysed. Several predictions from continuum theory are recovered in our simulations, in addition to further insight into the process by which cohesionless rubble piles can deform. Fundamentally different outcomes are found for frictionless grains and grains with surface friction modelled, verifying the importance of including such models in granular simulations. We find that the initiation of shape deformation is most consistently described by a Drucker–Prager failure criterion, which also provides an independent measure of the effective friction angle of our self-gravitating pile. Insight is also gained into the energetics of deformation, with most of the kinetic energy loss going into the deformation of the rubble pile, and a smaller component being internally dissipated. Finally, with this work we want to compare this computational approach with the theoretical predictions and, if possible, to mutually validate them.

Laser-induced reshaping of particles aiming at energy-saving applications

Submicrometer scaled spheres are realized by a laser-induced reshaping process. An irregular shaped particle absorbs the laser-energy and turns into a spherical liquid droplet dispersed in deionized water. Subsequently, the spherical liquid droplet is “frozen” by the fast cooling of the surrounding deionized water, giving rise to the formation of submicrometer scale spheres. This is a versatile, simple, low-cost, fast and high-throughput technique to prepare submicrometer scale spheres with multiple structural controlling capabilities. These submicrometer scale spheres show excellent friction coefficient-reduction (>50%) properties when they are used as lubricant oil additives, opening the door to the possibility of saving energy by reducing friction caused energy loss.

Effects of fourth-order fiber dispersion on ultrashort parabolic optical pulses in the normal dispersion regime

We propose a new method for the generation of both triangular-shaped optical pulses and flat-top, coherent supercontinuum spectra using the effect of fourth-order dispersion on parabolic pulses in a passive, normally dispersive highly nonlinear fiber. The pulse reshaping process is described qualitatively and is compared to numerical simulations.