Secondary Transition Research Articles

Suspension Taylor–Couette flow: co-existence of stationary and travelling waves, and the characteristics of Taylor vortices and spirals

Flow visualization and particle image velocimetry (PIV) measurements are used to unravel the pattern transition and velocity field in the Taylor–Couette flow (TCF) of neutrally buoyant non-Brownian spheres immersed in a Newtonian fluid. With increasing Reynolds number ($Re$) or the rotation rate of the inner cylinder, the bifurcation sequence in suspension TCF remains same as in its Newtonian counterpart (i.e. from the circular Couette flow (CCF) to stationary Taylor vortex flow (TVF) and then to travelling wavy Taylor vortices (WTV) with increasing $Re$) for small particle volume fractions ($\unicode[STIX]{x1D719}<0.05$). However, at $\unicode[STIX]{x1D719}\geqslant 0.05$, non-axisymmetric patterns such as (i) the spiral vortex flow (SVF) and (ii) two mixed or co-existing states of stationary (TVF, axisymmetric) and travelling (WTV or SVF, non-axisymmetric) waves, namely (iia) the ‘TVF$+$WTV’ and (iib) the ‘TVF$+$SVF’ states, are found, with the former as a primary bifurcation from CCF. While the SVF state appears both in the ramp-up and ramp-down experiments as in the work of Majji et al. (J. Fluid Mech., vol. 835, 2018, pp. 936–969), new co-existing patterns are found only during the ramp-up protocol. The secondary bifurcation TVF $\leftrightarrow$ WTV is found to be hysteretic or sub-critical for $\unicode[STIX]{x1D719}\geqslant 0.1$. In general, there is a reduction in the value of the critical Reynolds number, i.e. $Re_{c}(\unicode[STIX]{x1D719}\neq 0)<Re_{c}(\unicode[STIX]{x1D719}=0)$, for both primary and secondary transitions. The wave speeds of both travelling waves (WTV and SVF) are approximately half of the rotational velocity of the inner cylinder, with negligible dependence on $\unicode[STIX]{x1D719}$. The analysis of the radial–axial velocity field reveals that the Taylor vortices in a suspension are asymmetric and become increasingly anharmonic, with enhanced radial transport, with increasing particle loading. Instantaneous streamline patterns on the axial–radial plane confirm that the stationary Taylor vortices can indeed co-exist either with axially propagating spiral vortices or azimuthally propagating wavy Taylor vortices – their long-time stability is demonstrated. It is shown that the azimuthal velocity is considerably altered for $\unicode[STIX]{x1D719}\geqslant 0.05$, resembling shear-band type profiles, even in the CCF regime (i.e. at sub-critical Reynolds numbers) of suspension TCF; its possible role on the genesis of observed patterns as well as on the torque scaling is discussed.

Uncovering a novel transition in the dynamics of proteins in the dry state

The research of dynamics of protein is predominantly focused on the hydrated or solvated state, which is close to the physiological condition of biological relevance. Eclipsed by the hydrated and solvated counterparts, the dynamics of dry proteins are seldom studied in earnest. Studied occasionally, the data of dry proteins were not addressed, possibly due to the preconceived notion that dry proteins are bio inactive, and thus are uninteresting and unimportant. Actually lyophilized dry proteins are important for the pharmaceutical industry as the therapeutic proteins are often stored in lyophilized conditions to achieve long-term stability, which is of direct connection to the dynamics of protein in dry state. In order to uncover the intrinsic dynamics of dry proteins that previous studies overlooked or ignored, we analysed quasielastic neutron scattering, Mössbauer, and Brillouin light scattering data of various dry proteins. We demonstrate the existence of a novel transition of the dry protein dynamics at temperatures around 200 K, with the exact value dependent on the kind of protein. The transition temperature of dry proteins is found here independent of the time/frequency of the measurement, in stark contrast to the well-documented dynamical transition observed in hydrated proteins, the temperature of which is strongly depending on the time window probed experimentally. In addition we point out that this transition in dry proteins is analogous to those observed before in the glassy state of various glass-forming materials, the origin of which is the change of the caged molecule dynamics in response to the change of the temperature dependence of density when crossing the secondary glass transition temperature Tgβ for the Johari-Goldstein β-relaxation. We show that the transition of various dry proteins also occurs around Tgβ, thus suggesting that the underlying microscopic mechanism is the same as the one identified and explained before for many glass-formers of different types. The presence of the transition is independent of the trace amount of water in supposedly dry proteins, although the value of Tgβ can vary somewhat. The novel transition in dry proteins has impact on bio-pharmaceutical research and applications because of the connection to the Johari-Goldstein β-relaxation, which can affect long-term stability of lyophilized dry proteins.

Molecular Modeling of the PTF‐J and PTF‐L Heterotrimeric Complexes, 3‐D Printing, Overexpression, Purification and Structural Analysis of the Complexes using Cryo‐Electron Microscopy and Ptf1a gene Expression Patterns During Pancreas Development in Zebrafish

Dallas Independent School District biomedical research students study the master regulatory transcription factor heterotrimeric complexes PTF‐J and PTF‐L that are required for the early and late developmental cascade of the pancreas. The PTF‐J and PTF‐L complexes are composed of a common E‐box protein E12/47, Ptf1a. and either RbpJ or RbpL. The PTF‐J complex is required for the early developmental stage of the pancreas and during the secondary transition of pancreas development, RbpJ is replaced by RbpL generating the PTF‐L complex, which is required for the final maturation steps for the development of the exocrine pancreas. In the current studies biomedical research student utilized the known structures for RbpJ, RpbL, the MyoD bHLH domain and E12/47 bHLH domain to generate molecular models bound to the enhancer sequence found in genes regulated by the heterotrimeric complexes during pancreas development. The PTF‐J and PTF‐L enhancer sequence is composed of an E‐box sequence separated by one to three helical turns from a TC‐box sequence. Biomedical research students performed energy minimization of the complexes and generate a model using 3‐D printing technology. Biomedical research students also study the temporal and spatial expression patterns of the PTF‐J and PTF‐L complexes during pancreas development in Zebrafish using immunofluorescence. The overall goals the program are threefold: first, to expose enthusiastic high school students to an authentic hands‐on biomedical research project, second, to solve the structure of the complexes using Cryo‐Electron Microscopy and third to identify the temporal and spatial expression pattern of the Ptf1a protein during pancreas development in Zebrafish.Support or Funding InformationJunior League of DallasThis abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

A simple angle integration method for the determination of capture reaction cross sections

In order to determine the cross section of a reaction by the angular distribution method, it is essential to calculate the angular distributions of all secondary transitions that lead to the ground state. This is achieved by analysing spectra from HPGe detectors at various detection angles, which is a time consuming process. In this work, a simpler angle integration method is presented that allows to determine cross sections of capture reactions by measuring spectra at fewer detection angles.

Conductance Changes in Bovine Serum Albumin Caused by Drug-Binding Triggered Structural Transitions.

Proteins, due to their binding selectivity, are promising candidates for fabricating nanoscale bio-sensors. However, the influence of structural change on protein conductance caused by specific protein-ligand interactions and disease-induced degeneration still remains unknown. Here, we excavated the relationship between circular dichroism (CD) spectroscopy and conductive atomic force microscopy (CAFM) to reveal the effect of the protein secondary structures changes on conductance. The secondary structure of bovine serum albumin (BSA) was altered by the binding of drugs, like amoxicillin (Amox), cephalexin (Cefa), and azithromycin (Azit). The CD spectroscopy shows that the α-helical and β-sheet content of BSA, which varied according to the molar ratio between the drug and BSA, changed by up to 6%. The conductance of BSA monolayers in varying drug concentrations was further characterized via CAFM. We found that BSA conductance has a monotonic relation with α-helical content. Moreover, BSA conductance seems to be in connection with the binding ability of drugs and proteins. This work elucidates that protein conductance variations caused by secondary structure transitions are triggered by drug-binding and indicate that electrical methods are of potential application in protein secondary structure analysis.

Multiscale Computational Model for Particle Size Evolution during Coprecipitation of Li-Ion Battery Cathode Precursors.

Next generation lithium ion batteries require higher energy and power density, which can be achieved by tailoring the cathode particle morphology, such as particle size, size distribution, and internal porosity. All these morphological features are determined during the cathode synthesis process, which consists of two steps, (i) coprecipitation and (ii) calcination. Transition metal hydroxide precursors are synthesized during the coprecipitation process, whereas their oxidation and lithiation occur during calcination. The size and size distribution of crystalline primary and aggregated secondary particles and their internal porosity are determined during coprecipitation. Operating conditions of the chemical reactor, such as solution pH, ammonia concentration, and stirring speed control the final morphological features. Here, a multiscale computational model has been developed to capture the nucleation and growth of crystalline primary particles and their aggregation into secondary transition metal hydroxide precursor particles. The simulations indicate that increasing solution pH and decreasing ammonia concentration lead to smaller sizes of the secondary particles. A phase map has been developed that can help identify the synthesis conditions needed for a specified particle size and size distribution.

How Do Students Revisit School Mathematics in Modular Arithmetic? Conditions and Affordances of the Transition to Tertiary Mathematics with a Focus on Learning Processes

In the transition from secondary to tertiary mathematics, students try to participate in tertiary mathematics by replicating familiar school mathematical discourses. The objective of this case study is to investigate the conditions and affordances under which students proceed from familiar school mathematical discourses to new, tertiary discourses with a specific perspective on learning processes. The study was located in an upper secondary transition course in a teaching unit on elementary number theory in which highly proficient students in their penultimate year of schooling participated. The main finding is that there was not a linear progression towards the intended tertiary mathematical discourse of modular multiplication but a coexistence of two discourses developing in parallel: the intended tertiary discourse and a continuation of school mathematical discourses. Students see these two discourses as the same, connected by the same perceived aim of searching for patterns. Further hindering discursive development are utterances, in which elements of the intended tertiary discourse (words and representations) are used superfluously, so that elementary/secondary utterances appear to be tertiary. These findings illustrate the need to explicate and address metanarratives. Metanarratives can connect two discourses developing in parallel in ways that, in this case, hinder discursive development towards the intended tertiary discourse.

Phase transitions of antiferromagnetic Ising spins on the zigzag surface of an asymmetrical Husimi lattice.

An asymmetrical two-dimensional Ising model with a zigzag surface, created by diagonally cutting a regular square lattice, has been developed to investigate the thermodynamics and phase transitions on surface by the methodology of recursive lattice, which we have previously applied to study polymers near a surface. The model retains the advantages of simple formulation and exact calculation of the conventional Bethe-like lattices. An antiferromagnetic Ising model is solved on the surface of this lattice to evaluate thermal properties such as free energy, energy density and entropy, from which we have successfully identified a first-order order–disorder transition other than the spontaneous magnetization, and a secondary transition on the supercooled state indicated by the Kauzmann paradox.

Supporting the socio-emotional aspects of the primary–secondary transition for pupils with social, emotional and behavioural needs: Affordances and constraints

The primary–secondary transition presents both opportunities and challenges for children. For some, it may represent a ‘critical period’ which impacts their future mental health and well-being. This article focuses on identifying the affordances and constraints of a group-work approach to support children with social, emotional and behavioural needs (SEBN) across the transition with a specific focus on the socio-emotional aspects of transition. This evaluative, mixed-methods case study took place in six clusters of primary/secondary schools in Scotland involving 63 pupils who participated within support groups for around twenty 1-hour sessions. It focuses on the accounts of Support group Leaders, drawing from focus group discussions held within each cluster and a Likert-type scale questionnaire. A wide range of facilitators and barriers to implementation and to pupil progress were identified. Facilitators related principally to the quality of relationships and pedagogy which the support group afforded and the quality of support for the project. Barriers related principally to organisational and resource constraints and more general concerns around how behaviour support is perceived. The article argues that supporting the transition for pupils with SEBN is complex and there is no ‘magic bullet’. Building a supportive infrastructure from the outset is key to success.

Glycosaminoglycans Induce Amyloid Self-Assembly of a Peptide Hormone by Concerted Secondary and Quaternary Conformational Transitions.

Amyloids are polypeptide supramolecular assemblies that have been historically associated with numerous pathologies. Nonetheless, recent studies have identified many amyloid structures that accomplish vital physiological functions. Interestingly, amyloid fibrils, either pathological or functional, have been reported to be consistently associated with other biomolecules such as RNA and glycosaminoglycans (GAGs). These linear polyanions, RNA and GAGs, have also demonstrated an inherent ability to accelerate and/or promote amyloid formation. GAGs, including heparan sulfate, are highly charged polysaccharides that may have essential roles in the storage of peptide hormones in the form of amyloids. In this study, we evaluated the ability of sulfated GAGs to promote the self-assembly of the peptide (neuro)hormone PACAP27 and investigated the secondary and quaternary conformational transitions associated with the amyloidogenic process. PACAP27 readily self-assembled into insoluble, α-helix-rich globular particulates in the presence of sulfated GAGs, which gradually condensed and disappeared as nontoxic β-sheet-rich amyloid fibrils were formed. By designing a PACAP27 derivative for which helical folding was hindered, we observed that the α-helix-to-β-sheet conformational transition within the amorphous particulates constitutes the rate-limiting step of primary nucleation events. The proposed mechanism of GAG-induced self-assembly within insoluble particulates appears to be fundamentally different from usual amyloidogenic systems, which commonly implicates the formation of soluble prefibrillar proteospecies. Overall, this study provides new insights into the mechanistic details involved in the formation of functional amyloids catalyzed by polyanions, such as the assembly of nuclear amyloid bodies and the storage of peptide hormones.

Flow Behavior in Radial Vane Disk Brake Rotors at Low Rotational Speeds

The flow behavior through the vented channel of a brake disk determines its thermal performance, viz. its resistance to brake fade, brake wear, thermal distortion, and thermal cracking. We present experimental results of the flow characteristics inside the vented channel of a radial vane brake rotor with a selected number of vanes (i.e., 18, 36, and 72) but constant porosity (ε ∼ 0.8) at low rotational speeds (i.e., 25 rpm ≤ N ≤ 400 rpm). Using bulk flow and velocity field mapping measurement techniques, we observed that increasing the number of vanes for a given rotational speed results in (i) the increase in the mass flow rate of the air pumped by the rotor, (ii) the reduction of inflow angle (β) becoming more closely aligned with the vanes, (iii) more uniformly distributed passage velocity profiles, and (iv) increased Rossby number. In addition, for a certain range of rotational speeds (i.e., 100 rpm ≤ N ≤ 400 rpm), we identified the biased development of streamwise secondary flow structures in the vented passages that only form on the inboard side of the rotor. This is due to the entry conditions where the incoming flow must transition sharply from the axial to the radial direction as air is drawn into the rotating channel. The biased secondary flow is likely to cause uneven cooling of the brake rotor, leading to thermal distortion. At lower rotational speeds (i.e., N < 100 rpm), the biased secondary flows transitions into a symmetric structure.

Fundamental movement skills and their relationship with measures of health-related physical fitness of primary school children prior to secondary school transition: a Welsh perspective

ABSTRACTThe aims of this study were to investigate levels of fundamental movement skills (FMS) proficiency and their relationship with measures of health-related physical fitness of primary school children prior to their transition to high school in Wales. The results demonstrated that overall levels of FMS proficiency with these children were low with significant differences existing between the genders. In addition, the measures of health-related physical fitness significantly correlated with FMS proficiency in both genders. In summary, these findings suggest that primary school children lack the foundational elements to support their transition to high school physical education.

Essential Role of Protein Arginine Methyltransferase 1 in Pancreas Development by Regulating Protein Stability of Neurogenin 3.

BackgroundProtein arginine methyltransferase 1 (PRMT1) is a major enzyme responsible for the formation of methylarginine in mammalian cells. Recent studies have revealed that PRMT1 plays important roles in the development of various tissues. However, its role in pancreas development has not yet been elucidated.MethodsPancreatic progenitor cell-specific Prmt1 knock-out (Prmt1 PKO) mice were generated and characterized for their metabolic and histological phenotypes and their levels of Neurog3 gene expression and neurogenin 3 (NGN3) protein expression. Protein degradation assays were performed in mPAC cells.ResultsPrmt1 PKO mice showed growth retardation and a severely diabetic phenotype. The pancreatic size and β-cell mass were significantly reduced in Prmt1 PKO mice. Proliferation of progenitor cells during the secondary transition was decreased and endocrine cell differentiation was impaired. These defects in pancreas development could be attributed to the sustained expression of NGN3 in progenitor cells. Protein degradation assays in mPAC cells revealed that PRMT1 was required for the rapid degradation of NGN3.ConclusionPRMT1 critically contributes to pancreas development by destabilizing the NGN3 protein.

The population genomics of multiple tsetse fly (Glossina fuscipes fuscipes) admixture zones in Uganda.

Understanding the mechanisms that enforce, maintain or reverse the process of speciation is an important challenge in evolutionary biology. This study investigates the patterns of divergence and discusses the processes that form and maintain divergent lineages of the tsetse fly Glossina fuscipes fuscipes in Uganda. We sampled 251 flies from 18 sites spanning known genetic lineages and the four admixture zones between them. We apply population genomics, hybrid zone and approximate Bayesian computation to the analysis of three types of genetic markers: 55,267 double-digest restriction site-associated DNA (ddRAD) SNPs to assess genome-wide admixture, 16 microsatellites to provide continuity with published data and accurate biogeographic modelling, and a 491-bp fragment of mitochondrial cytochrome oxidase I and II to infer maternal inheritance patterns. Admixture zones correspond with regions impacted by the reorganization of Uganda's river networks that occurred during the formation of the West African Rift system over the last several hundred thousand years. Because tsetse fly population distributions are defined by rivers, admixture zones likely represent both old and new regions of secondary contact. Our results indicate that older hybrid zones contain mostly parental types, while younger zones contain variable hybrid types resulting from multiple generations of interbreeding. These findings suggest that reproductive barriers are nearly complete in the older admixture zones, while nearly absent in the younger admixture zones. Findings are consistent with predictions of hybrid zone theory: Populations in zones of secondary contact transition rapidly from early to late stages of speciation or collapse all together.

Research on High Efficiency V/f Control of Segment Winding Permanent Magnet Linear Synchronous Motor

By analyzing the relationship between the electromagnetic parameters and the secondary position during the primary and secondary coupling transition of the segment winding permanent magnet linear synchronous motor (SW-PMLSM), the variable parameter mathematical model of the rotor side of the SW-PMLSM is established. Taking the three-stage primary lifting system as an example, the dynamic process of the whole system is simulated and analyzed. According to the characteristics of its parameters, the segmentation vector control is obtained as the best stability control method. However, in practical applications, in order to save costs, the segmented linear motor often adopts the effective section parallel power supply mode, and the SW-PMLSM parallel power supply model is obtained by approximate simplification. This paper proposes a SW-PMLSM high-efficiency V/f control method, which combines the advantages of traditional V/f control and field-oriented control. It does not need to install position sensor, and can realize simple and high-performance motor drive. Finally, simulation and experimental results are provided to validate the effectiveness of the fidelity of the proposed strategy.

Strategies for Developing Work Experiences for Youth With Intellectual and Developmental Disabilities

High school work experience is a predictor of postsecondary employment success for youth with intellectual and developmental disabilities (IDD). Developing integrated work experiences often requires schools to partner with local businesses; yet, secondary special education transition teams may not have prior experience or preparation in this type of transition work. Drawing on supported employment research, this article provides transition specialists and secondary special educators with practical strategies for identifying and engaging with potential local business partners and creating networking opportunities that build effective relationships.

Continuation and stability of rotating waves in the magnetized spherical Couette system: secondary transitions and multistability.

Rotating waves (RW) bifurcating from the axisymmetric basic magnetized spherical Couette (MSC) flow are computed by means of Newton-Krylov continuation techniques for periodic orbits. In addition, their stability is analysed in the framework of Floquet theory. The inner sphere rotates while the outer is kept at rest and the fluid is subjected to an axial magnetic field. For a moderate Reynolds number Re = 103 (measuring inner rotation), the effect of increasing the magnetic field strength (measured by the Hartmann number Ha) is addressed in the range Ha∈(0, 80) corresponding to the working conditions of the HEDGEHOG experiment at Helmholtz-Zentrum Dresden-Rossendorf. The study reveals several regions of multistability of waves with azimuthal wavenumber m = 2, 3, 4, and several transitions to quasi-periodic flows, i.e modulated rotating waves. These nonlinear flows can be classified as the three different instabilities of the radial jet, the return flow and the shear layer, as found in the previous studies. These two flows are continuously linked, and part of the same branch, as the magnetic forcing is increased. Midway between the two instabilities, at a certain critical Ha, the non-axisymmetric component of the flow is maximum.

Structure-property relationships for wet dentin adhesive polymers.

Dentin adhesive systems for composite tooth restorations are composed of hydrophilic/hydrophobic monomers, solvents, and photoinitiators. The adhesives undergo phase separation and concomitant compositional change during their application in the wet oral environment; phase separation compromises the quality of the hybrid layer in the adhesive/dentin interface. In this work, the adhesive composition in the hybrid layer can be represented using the phase boundaries of a ternary phase diagram for the hydrophobic monomer/hydrophilic monomer/water system. The polymer phases, previously unaccounted for, play an important role in determining the mechanical behavior of the bulk adhesive, and the chemomechanical properties of the phases are intimately related to the effects produced by differences in the hydrophobic-hydrophilic composition. As the composition of the polymer phases varies from hydrophobic-rich to hydrophilic-rich, the amount of the adsorbed water and the nature of polymer-water interaction vary nonlinearly and strongly correlate with the change in elastic moduli under wet conditions. The failure strain, loss modulus, and glass transition temperature vary nonmonotonically with composition and are explained based upon primary and secondary transitions observed in dynamic mechanical testing. Due to the variability in composition, the assignment of mechanical properties and the choice of suitable constitutive models for polymer phases in the hybrid layer are not straightforward. This work investigates the relationship between composition and chemomechanical properties of the polymer phases formed on the water-adhesive phase boundary using quasistatic and dynamic mechanical testing, mass transfer experiments, and vibrational spectroscopy.

Possible flexoelectric origin of the Lifshitz transition in LaAlO3/SrTiO3 interfaces

Multiple experiments have observed a sharp transition in the band structure of LaAlO$_3$/SrTiO$_3$ (001) interfaces as a function of applied gate voltage. This Lifshitz transition, between a single occupied band at low electron density and multiple occupied bands at high density, is remarkable for its abruptness. In this work, we propose a mechanism by which such a transition might happen. We show via numerical modeling that the simultaneous coupling of the dielectric polarization to the interfacial strain ("electrostrictive coupling") and strain gradient ("flexoelectric coupling") generates a thin polarized layer whose direction reverses at a critical density. The Lifshitz transition occurs concomitantly with the polarization reversal and is first-order at $T=0$. A secondary Lifshitz transition, in which electrons spread out into semiclassical tails, occurs at a higher density.

High–pressure electrical conductivity and Raman spectroscopy of chalcanthite

The phase transitions and dehydration of chalcanthite were investigated by electrical conductivity and Raman spectroscopy at 1.0–24.0 GPa and 293–673 K in a diamond anvil cell. At ambient temperature, two secondary phase transitions were observed according to discontinuous changes in the slope of Raman shifts, full width at half maximum and electrical conductivities at ∼7.3 and ∼10.3 GPa. The dehydration temperatures were determined by the splitting of Raman peaks and changes in electrical conductivity as ∼350 and ∼500 K at respective ∼3.0 and ∼6.0 GPa. A positive relationship for chalcanthite between dehydration temperature and pressure is established.