Dynamic Condensation Research Articles

Dynamics of hierarchical beam lattice structures by an exact reduced-order dynamic-stiffness model

An exact reduced-order dynamic-stiffness model is proposed to study the dynamics of two-dimensional hierarchical beam lattices. Upon modelling every member of the lattice by a single exact two-node beam element, the model retains a few primary nodes of the unit cell and involves an exact dynamic condensation of the nodal degrees of freedom of the lattice structure internal to the unit cell and connected to the primary nodes. It is shown that the modes of the reduced-order model exhibit two orthogonality conditions, with dynamic-stiffness terms pertinent to the condensed lattice structures. The orthogonality conditions are the basis to decouple the motion equations and derive the exact modal response to external loading, in both time and frequency domains, under the assumption of proportional damping. The modal response is obtained in simple and elegant analytical form for the whole lattice, including the condensed lattice structures internal to the unit cells. Moreover, it can be calculated very expeditiously thanks to an exact representation of the eigenfunctions based on frequency dependent shape functions, which applies regardless of geometry and complexity of the hierarchical lattice structure. Numerical results confirm the exactness of the proposed reduced-order dynamic-stiffness model by comparison with standard finite-element solutions in ABAQUS.

CASC3 Biomolecular Condensates Restrict Turnip Crinkle Virus by Limiting Host Factor Availability

The exon-junction complex (EJC) plays a role in post-transcriptional gene regulation and exerts antiviral activity towards several positive-strand RNA viruses. However, the spectrum of RNA viruses that are targeted by the EJC or the underlying mechanisms are not well understood. EJC components from Arabidopsis thaliana were screened for antiviral activity towards Turnip crinkle virus (TCV, Tombusviridae). Overexpression of the accessory EJC component CASC3 inhibited TCV accumulation > 10-fold in Nicotiana benthamiana while knock-down of endogenous CASC3 resulted in a > 4-fold increase in TCV accumulation. CASC3 forms cytoplasmic condensates and deletion of the conserved SELOR domain reduced condensate size 7-fold and significantly decreased antiviral activity towards TCV. Mass spectrometry of CASC3 complexes did not identify endogenous stress granule or P-body markers and CASC3 failed to co-localize with an aggresome-specific dye suggesting that CASC3 condensates are distinct from well-established membraneless compartments. Mass spectrometry and bimolecular fluorescence complementation assays revealed that CASC3 sequesters Heat shock protein 70 (Hsp70-1) and Glyceraldehyde-3-phosphate dehydrogenase (GAPDH), two host factors with roles in tombusvirus replication. Overexpression of Hsp70-1 or GAPDH reduced the antiviral activity of CASC3 2.1-fold and 2.8-fold, respectively, and suggests that CASC3 inhibits TCV by limiting host factor availability. Unrelated Tobacco mosaic virus (TMV) also depends on Hsp70-1 and CASC3 overexpression restricted TMV accumulation 4-fold and demonstrates that CASC3 antiviral activity is not TCV-specific. Like CASC3, Auxin response factor 19 (ARF19) forms poorly dynamic condensates but ARF19 overexpression failed to inhibit TCV accumulation and suggests that CASC3 has antiviral activities that are not ubiquitous among cytoplasmic condensates.

Dynamics of Bose-Einstein condensation in an asymmetric double-well potential

Josephson effect of Bose-Einstein condensate in double-well potential is an obvious manifestation of macroscopic quantum coherence. Most of researches focus on the symmetric double-well potential. In this work, we investigate the dynamic of Bose-Einstein condensates in an asymmetric double-well potential by using two-mode theory and computer simulation. In the absence of the interaction between atoms, the dynamic equation of condensate can be solved analytically. The amplitude as a function of energy difference of two wells is obtained. We can find that the change of energy difference will lead to the different dynamic behaviors of condensate. If the energy difference is relatively large, the condensate will primarily occupy the well that is occupied more than the other well at the beginning time. It is interesting that such a trap phenomenon is not dependent on the position of the high energy potential well nor the position of low energy potential well. If the energy difference becomes small, the tunneling and oscillation of condensate will be enhanced. When the interaction between atoms is present, our numerical calculations show that as the nonlinear interaction increases, the dynamic behavior of condensate exhibits different characteristics, such as trapping in a well, enhancing the tunneling and oscillation between two wells, and enhancing the trapping in a well at large nonlinear interaction, which is similar to the dynamic change caused by the energy difference in the case of ideal condensate. That is to say, on the one hand, the nonlinear interaction can lead to the trap of condensate as well as the dynamic trap to happen in symmetric double-well potential. On the other hand, the nonlinearity can promote the tunneling of condensate, counteracting the effect of the asymmetry of potential. And, this counteracting effect is related to the difference in energy between asymmetric potential wells. To understand the underlying mechanism, the full dynamic behavior of two-mode model is illustrated and the dynamic transition can be seen clearly. Combining the results obtained with and without interaction, regarding nonlinear interaction as effective potential provides a clear way to explain dynamic transition of condensate in an asymmetric double-well potential. In addition, we also perform the numerical simulations of the Gross-Pitaevskii equation, and the results are consistent with the conclusions obtained by using the two-mode theory.

Rabies virus P protein binds to TBK1 and interferes with the formation of innate immunity-related liquid condensates

Viruses must overcome the interferon-mediated antiviral response to replicate and propagate into their host. Rabies virus (RABV) phosphoprotein P is known to inhibit interferon induction. Here, using a global mass spectrometry approach, we show that RABV P binds to TBK1, a kinase located at the crossroads of many interferon induction pathways, resulting in innate immunity inhibition. Mutations of TBK1 phosphorylation sites abolish P binding. Importantly, we demonstrate that upon RABV infection or detection of dsRNA by innate immunity sensors, TBK1 and its adaptor proteins NAP1 and SINTBAD form dynamic cytoplasmic condensates that have liquid properties. These condensates can form larger aggregates having ring-like structures in which NAP1 and TBK1 exhibit locally restricted movement. P binding to TBK1 interferes with the formation of these structures. This work demonstrates that proteins of the signaling pathway leading to interferon induction transiently form liquid organelles that can be targeted by viruses.

ARF19 Condensation in the Arabidopsis Stomatal Lineage.

The phytohormone auxin regulates nearly every aspect of plant development. Transcriptional responses to auxin are driven by the activities of the AUXIN RESPONSE FACTOR family of transcription factors. ARF19 (AT1G19220) is critical in the auxin signaling pathway and has previously been shown to undergo protein condensation to tune auxin responses in the root. However, ARF19 condensation dynamics in other organs has not yet been described. In the Arabidopsis stomatal lineage, we found that ARF19 cytoplasmic condensates are enriched in guard cells and pavement cells, terminally differentiated cells in the leaf epidermis. This result is consistent with previous studies showing ARF19 condensation in mature root tissues. Our data reveal that the sequestration of ARF19 into cytoplasmic condensation in differentiated leaf epidermal cells is similar to root-specific condensation patterns.

Numerical modeling of natural vibrations of coaxial shells partially filled with fluid, taking into account the effects on the free surface

This work is devoted to the numerical analysis of vertical elastic coaxial cylindrical shells completely or partially filled with a quiescent compressible fluid with account for sloshing of its free surface. The problem is solved in the axisymmetric formulation using a semi-analytical version of the finite element method. The fluid medium is described by the wave equation, which together with the conditions prescribed at its boundaries is reduced to the weak form by the Bubnov - Galerkin method. A mathematical formulation of the dynamic problem for thin-walled structures is developed using the variational principle of virtual displacements and linear theory of thin shells based on Kirchhoff - Love hypotheses. The fluid pressure on the walls of the structure is calculated according to Bernoulli's equation. Sloshing modes caused by gravitational effects on free surface of liquid medium are excluded from the resulting system of equations through the use of the iteration dynamic condensation method. The numerical model has been verified by comparing it with the known data for the case of a single shell partially filled with fluid. The influence of the fluid level on the lowest natural frequencies of the system vibrations at different variants of kinematic boundary conditions for shells (rigid clamping at both edges, cantilever support) and different widths of the annular gap between them has been evaluated. It has been found that for the examined configurations, the level of the fluid in the annular channel has a stronger influence on the frequency spectrum compared to the level of fluid in the cavity of the inner shell due to the fact that vibration frequencies change in a wider range.

A hybrid analytic–numerical formulation for the vibration analysis of a cylindrical shell coupled with an internal flexural floor structure

A hybrid analytic–numerical formulation is developed to study the vibration behaviors of a cylindrical shell coupled with an internal flexural floor structure. The full structure is divided into a cylindrical shell, axisymmetric annular plates and a non-axisymmetric floor structure. The cylindrical shell and annular plates are analyzed by the analytic dynamic stiffness method (DSM) while the floor is modeled by the finite element method (FEM), so the line connections between the cylindrical shell and interior floor degrade into discrete point connections. At each coupling point, virtual springs are used to couple the cylindrical shell and interior floor, and coupling conditions at six Dofs are fully taken into consideration. In DSM, the displacement solutions of the cylindrical shell and annular plate are described by exponential functions and Bessel functions, respectively. In FEM, the dynamic condensation technique is adopted to reduce the model Dofs, while the main dynamic characteristic of the FEM model is preserved as much as possible.To verify the accuracy and effectiveness of present formulation, vibration results calculated by present method are compared with those obtained from FEM and a test experiment. Moreover, the effects of ribs, bulkheads, coupling conditions, boundary conditions of the shell and structural damping on the vibration responses are also investigated.

U2AF1 Splicing Factor Mutations Affect RNA Subcellular Compartmentalization in Myeloid Malignancies

Myelodysplastic syndromes (MDS) are a group of clonal hematopoietic disorders characterized by morphological dysplasia, cytopenias and high risk of progression to acute myeloid leukemia (AML). Despite recent improvements in treatment strategies, the 5-year relative survival rate in MDS remains only 31%, dropping to 24% in AML. This highlights the need for a deeper characterization of the pathogenic mechanisms driving disease development and progression. Splicing factor (SF) mutations are the most common genetic abnormality in MDS and secondary AML. These mutations, in particular U2AF1 mutations, are associated with increased risk of AML transformation and poor survival. U2AF1 S34F and Q157R mutations determine RNA splicing alterations that eventually result in ineffective hematopoiesis. However, molecular mechanisms and biological consequences underlying the clonal advantage of SF-mutant over wildtype cells remain to be fully elucidated. To address this aim, we recently combined high-resolution transcriptomics and imaging techniques in preclinical models of U2AF1-mutant and wildtype MDS/AML (Biancon et al., Mol Cell 2022). Our results showed that U2AF1 mutations cause widespread RNA binding and splicing alterations that directly affect the biology of RNA granules, i.e. dynamic condensates of RNAs and RNA binding proteins implicated in RNA metabolism, signaling and gene regulation. In particular, in U2AF1-mutant vs WT cell lines and primary cells we observed increased formation of stress granules (SGs), cytoplasmic RNA granules mediating cellular adaptation to stress conditions. Crucially, the enhanced stress response in U2AF1-mutant cells was associated with improved cell fitness, that was reverted by SG inhibition. Dysregulation of SGs, and potentially of other subcellular RNA condensates, may therefore represent a novel therapeutic vulnerability in MDS/AML patients carrying U2AF1 mutations. We here integrated single-cell (sc)RNA-seq data to further support the direct link between the U2AF1-mutant genotype and the increased SG phenotype in myeloid malignancies. We first isolated CD34+ blasts from bone marrow samples of MDS patients with (n=3) or without (n=3) U2AF1 S34F mutation. We then performed 10x Genomics scRNA-seq obtaining an average of 3,478 sequenced cells per sample for downstream analyses. Cells from different patients were integrated with Seurat v4.0.1 and annotated with the recently released Cell Marker Accordion (https://github.com/TebaldiLab/TheCellMarkerAccordion), confirming the expected skewing towards granulocyte-monocyte progenitor cells and erythroid lineage in S34F-mutant patients. Single cells were subsequently classified according to the detection of the S34F mutation (VarTrix v1.1.19), into: "WT" (WT cells in U2AF1-WT patients), "S34F_WT" (WT cells in U2AF1-S34F patients), "S34F" (S34F-mutant cells in U2AF1-S34F patients). Each cell was also associated to an "SG expression score", measuring the collective abundance of 149 transcripts enriched in SGs and aberrantly bound-spliced by mutant U2AF1 (Biancon et al., Mol Cell 2022). Importantly, S34F-mutant cells represented the category with the highest SG expression score (Figure 1A), consistently indicating an increased stress adaptation that might explain the clonal advantage of splicing factor-mutant cells in MDS. To further understand the effect of U2AF1-mutant binding and splicing alterations on other RNA condensates, we focused on Cajal bodies (CBs), nuclear granules involved in snRNA transcription and assembly of spliceosomal RNPs. Immunofluorescence (IF) staining for coilin, a known CB marker, followed by confocal imaging revealed a decrease in the number of CBs in U2AF1 S34F vs WT myeloid cell lines (Figure 1B). Of note, IF data were supported by RNA-seq data performed in the same cellular system (Biancon et al., Mol Cell2022), showing a significantly lower expression of snRNAs in U2AF1 mutant vs WT cells. The role of CBs in cancer is currently unknown, but the disruption of CBs may be associated to altered RNA splicing kinetics and increased genomic instability. Collectively, our results suggest that U2AF1 mutations affect the compartmentalization and aggregation properties of targeted RNAs, providing the rational to further investigate RNA granule perturbations in splicing factor-mutant myeloid malignancies for therapeutic potential. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

The effective theory of gravity and dynamical vacuum energy

Gravity and general relativity are considered as an Effective Field Theory (EFT) at low energies and macroscopic distances. The effective action of the conformal anomaly of light or massless quantum fields has significant effects on macroscopic scales, due to associated light cone singularities that are not captured by an expansion in local curvature invariants. A compact local form for the Wess-Zumino effective action of the conformal anomaly and stress tensor is given, requiring the introduction of a new light scalar field, which it is argued should be included in the low energy effective action for gravity. This scalar conformalon couples to the conformal part of the spacetime metric and allows the effective value of the vacuum energy, described as a condensate of an exact 4-form abelian gauge field strength F = dA, to change in space and time. This is achieved by the identification of the torsion dependent part of the Chern-Simons 3-form of the Euler class with the gauge potential A, which enters the effective action of the conformal anomaly as a J · A interaction analogous to electromagnetism. The conserved 3-current J describes the worldtube of 2-surfaces that separate regions of differing vacuum energy. The resulting EFT thus replaces the fixed constant Λ of classical gravity, and its apparently unnaturally large sensitivity to UV physics, with a dynamical condensate whose ground state value in empty flat space is Λeff = 0 identically. By allowing Λeff to vary rapidly near the 2-surface of a black hole horizon, the proposed EFT of dynamical vacuum energy provides an effective Lagrangian framework for gravitational condensate stars, as the final state of complete gravitational collapse consistent with quantum theory. The possible consequences of dynamical vacuum dark energy for cosmology, the cosmic coincidence problem, and the role of conformal invariance for other fine tuning issues in the Standard Model are discussed.

A Review of the Accuracy of Primal Assembly Model Order Reduction Techniques

Model order reduction (MOR) techniques have been used in structural dynamics for over sixty years as a quick and effective way to examine the dynamic behavior of complex finite element (FE) models. Various macroscopic phenomena arise from the physics and mechanics of the underlying microstructure, and MOR approaches can be employed in conjunction with the multiscale computational homogenization approach, which is deriving local macroscopic constitutive responses from underlying microstructure; to predict the dynamic behavior of heterogeneous macrostructures. The accuracy and efficiency of the most representative approaches from dynamic condensation, component mode synthesis (CMS), and general model reduction (GMR) methods are compared in this paper. The techniques considered are Guyan and the improved reduced system (IRS) from classical dynamic condensation, Craig-Bampton (CB) and enhanced Craig-Bampton (ECB) from CMS, IRS-based substructuring, GMR, and GMRPlus. All the substructuring methods employ primal assembly at the boundary interface of the substructures. The accuracy and computing efficiency of the techniques are compared in-depth using real-world engineering problems, and the effect of the number of substructures on the accuracy and computational cost is also examined.

Molecular dynamics simulation of steady-state droplet condensation on a fiber in direct contact membrane distillation settings

Understanding the dynamics of droplet condensation–evaporation behavior on fibers is important for improving the performance of fibrous membranes that are used in water purification applications, e.g., Direct Contact Membrane Distillation (DCMD). DCMD is a promising method of purifying water when low-grade waste heat or renewable energies are available. However, DCMD suffers from low throughput mass flux, and it is also prone to membrane flooding. We used molecular dynamics simulations in this work as the conventional (experimental or computational) methods do not have the required atomistic resolution to reveal the dynamics of water condensation–evaporation on the surface of fibers. Our simulations indicate that vapor flux across the membrane remains constant (with no droplet formation on the fiber) when the fibers’ Young–Laplace Contact Angle (YLCA) is greater than a critical value at which condensation is suppressed. However, mass flux decreases with time at lower YLCAs due to the formation and growth of water droplets on the fibers, which could ultimately lead to membrane flooding. We also studied the impact of feed temperature, permeate temperature, fiber diameter, fiber position, and domain size on the fiber critical YLCA. Optimizing these parameters allows the use of a wide array of materials in membrane fabrication, including even hydrophilic materials, while preventing membrane flooding and also enhancing mass flux. In this work, we also present a novel methodology to simulate steady-state droplet condensation–evaporation process in the framework of molecular dynamics simulation, i.e., simulation times >∼10 ns, in contrast to the quasi-steady-state simulations (simulation time <∼2 ns) reported in most previous studies. Our work demonstrates a simulation platform to study the dynamics of the water condensation–evaporation on fibers and can be used to guide the design of DCMD membranes.

Head-to-tail polymerization by VEL proteins underpins cold-induced Polycomb silencing in flowering control.

Transcriptional silencing through the Polycomb silencing machinery utilizes a "read-write" mechanism involving histone tail modifications. However, nucleation of silencing and long-term stable transmission of the silenced state also requires P-olycomb Repressive Complex 2 (PRC2) accessory proteins, whose molecular role is poorly understood. The Arabidopsis VEL proteins are accessory proteins that interact with PRC2 to nucleate and propagate silencing at the FLOWERING LOCUS C (FLC) locus, enabling early flowering in spring. Here, we report that VEL proteins contain a domain related to an atypical four-helix bundle that engages in spontaneous concentration-dependent head-to-tail polymerization to assemble dynamic biomolecular condensates. Mutations blocking polymerization of this VEL domain prevent Polycomb silencing at FLC. Plant VEL proteins thus facilitate assembly of dynamic multivalent Polycomb complexes required for inheritance of the silenced state.

Lipid Surfaces and Glutamate Anions Enhance Formation of Dynamic Biomolecular Condensates Containing Bacterial Cell Division Protein FtsZ and Its DNA-Bound Regulator SlmA.

Dynamic biomolecular condensates formed by liquid-liquid phase separation can regulate the spatial and temporal organization of proteins, thus modulating their functional activity in cells. Previous studies showed that the cell division protein FtsZ from Escherichia coli formed dynamic phase-separated condensates with nucleoprotein complexes containing the FtsZ spatial regulator SlmA under crowding conditions, with potential implications for condensate-mediated spatiotemporal control of FtsZ activity in cell division. In the present study, we assessed formation of these condensates in the presence of lipid surfaces and glutamate ions to better approximate the E. coli intracellular environment. We found that potassium glutamate substantially promoted the formation of FtsZ-containing condensates when compared to potassium chloride in crowded solutions. These condensates accumulated on supported lipid bilayers and eventually fused, resulting in a time-dependent increase in the droplet size. Moreover, the accumulated condensates were dynamic, capturing protein from the external phase. FtsZ partitioned into the condensates at the lipid surface only in its guanosine diphosphate (GDP) form, regardless of whether it came from FtsZ polymer disassembly upon guanosine triphosphate (GTP) exhaustion. These results provide insights into the behavior of these GTP-responsive condensates in minimal membrane systems, which suggest how these membraneless assemblies may tune critical bacterial division events during the cell cycle.

Condensation and thermalization of an easy-plane ferromagnet in a spinor Bose gas

The extensive control of spin makes spintronics a promising candidate for future scalable quantum devices. For the generation of spin-superfluid systems, a detailed understanding of the build-up of coherence and relaxation is necessary. However, to determine the relevant parameters for robust coherence properties and faithfully witnessing thermalization, the direct access to space- and time-resolved spin observables is needed. Here, we study the thermalization of an easy-plane ferromagnet employing a homogeneous one-dimensional spinor Bose gas. Building on the pristine control of preparation and readout we demonstrate the dynamic emergence of long-range coherence for the spin field and verify spin-superfluidity by experimentally testing Landau's criterion. We reveal the structure of the emergent quasi-particles: one 'massive'(Higgs) mode, and two 'massless' (Goldstone) modes - a consequence of explicit and spontaneous symmetry breaking, respectively. Our experiments allow for the first time to observe the thermalization of an easy-plane ferromagnetic Bose gas; we find agreement for the relevant momentum-resolved observables with a thermal prediction obtained from an underlying microscopic model within the Bogoliubov approximation. Our methods and results pave the way towards a quantitative understanding of condensation dynamics in large magnetic spin systems and the study of the role of entanglement and topological excitations for its thermalization.

A highly reusable fluorescent nanofilm sensor enables high-performance detection of ClO2

As the most effective disinfectant, the safe-use of ClO2 is based on proper concentrations. A big challenge in the determination of ClO2 lies in reusability owing to its strong oxidative property. Herein, we report for the first time a nanofilm-based fluorescent sensor towards the high-performance detection of ClO2. The nanofilm was prepared via interfacially confined dynamic covalent condensation of a fluorescent o-carborane derivative (CB-2CHO) and calix[4]arenetetrahydrazide (CATH). The nanofilm as obtained is smooth and uniform. The thickness can be tuned at least from 80 nm to 400 nm. Meanwhile, the nanofilm is photochemically stable, and shows a Stocks shift of 193 nm. A fluorescent sensor constructed with the nanofilm depicted fast, sensitive, selective, and fully reversible sensing to ClO2 vapor in air. Moreover, non-invasive detection of the chemical in aqueous phase with a detection limit of ∼0.85 mg/L was realized via vapor sampling from the headspace of the solution. The linear range is from a few to 5000 mg/L.

Design and Experimental Investigations on the Helium Circulating Cooling System Operating at Around 20 K for a 300-kvar Class HTS Dynamic Synchronous Condenser

A project to develop a 10-Mvar high temperature-superconducting (HTS) dynamic synchronous condenser (DSC) is carried out by China Southern Power Grid Corporation. In order to cool the magnets to 20–30 K, a set of cryogenic system using circulating helium as the working fluid was developed, and it has been coupled and tested with the 300-kvar class dynamic synchronous condenser. Three cryogenic coolers are used as the cold source to provide more than 120 W@20 K cooling power. Cryogenic helium pump is employed to overcome a pressure drop of about 2.5 kPa induced by the helium gas circulating in the transfer tubes and heat exchangers. In the static tests coupled with the 300-kvar class dynamic synchronous condenser, the entire magnet was cooled to approximately 26.2 K by about 5 days. Once the rotor speeds up and reaches the design value of operation, the temperature rises slightly to about 26.6 K. Nowadays, the cooling system is upgrading and it will be served for the developed 10-Mvar DSC in the next year.

Application Prospects of the Superconducting Dynamic Synchronous Condenser

The new power system based on renewable energy sources may bring the problems of voltage and frequency stability due to the high-level power electronic-based interfaced generation. As a reliable reactive power compensation equipment, dynamic synchronous condensers (DSCs) have the merits of short response time and high overload capacity. They can also improve the system inertia and short-circuit current capacity, and play the role of voltage and frequency stabilizer in the power system. Compared with the conventional DSCs, the superconducting DSCs have higher efficiency, stronger voltage support ability and more excellent reactive compensation performance. In 2018, a research project was launched to explore the feasibility of the superconducting DSC in power grid. The project has achieved significant progress. A hundred-kW prototype was designed and made for technical verification, and the design procedure of the 10 Mvar one is being carried out.

Tutorial: Dynamic organic growth modeling with a volatility basis set

Organic aerosols are ubiquitous in the atmosphere and oxygenated organics are a major driver of aerosol growth. The volatility basis set (VBS) as introduced by Donahue et al. (2006, 2011) is often used to simplify the partitioning behavior of the huge variety of atmospheric organics. Recently, the VBS was used to dynamically model aerosol growth from the smallest sizes onwards. This tutorial is intended to equip the reader with the necessary tools to facilitate organic growth modelling based on gas-phase measurements of oxygenated organics using a 2-dimensional VBS. We start with a contextualization of the VBS in partitioning theory and point out the need for dynamic modeling. We provide an overview on the most common methods to estimate the volatility of oxygenated organics and give detailed instruction on how to construct the binned VBS. We then explain the dynamic condensation model including solution and curvature effects. Furthermore, we provide a python package for VBS growth calculations and show with two examples from ambient and chamber measurements how growth rates can be calculated. Last, we summarize the limitation of this approach and outline necessary future developments.

On the Forced Vibration of Bending-Torsional-Warping Coupled Thin-Walled Beams Carrying Arbitrary Number of 3-DoF Spring-Damper-Mass Subsystems

This paper presents an analytical transfer matrix modeling framework for the forced vibration of a bending-torsional-warping coupling Euler-Bernoulli thin-walled beam carrying an arbitrary number of three degree-of-freedom (DOF) spring-damper-mass (SDM) subsystems. The thin-walled beam is divided into a series of distinct sub-beams whose ends are connected to the SDM subsystems. The transfer matrix for each sub-beam is developed based on the exact shape functions of the bending-torsional-warping coupling Euler-Bernoulli theory. Each SDM system is modelled by a set of effective springs based on the dynamic condensation method. The governing matrix equation is formulated based on the compatibility conditions of the placement and the force at the common interfaces of two adjacent sub-beams. Then, a closed-form expression for the frequency response function of the thin-walled beam system is proposed. The results computed by the proposed method achieve good agreement with those obtained by the conventional finite-element method, which shows the accuracy and reliability of the proposed method. The effects of the system parameters on the vibration transmission and vibration isolation properties of the thin-walled beam system are studied. The presented method can simultaneously consider arbitrary number of SDM subsystems and boundary conditions. Furthermore, none of the associated matrices are larger than 12 × 12, which provides a significant computational advantage.

Buildup dynamics of room-temperature polariton condensation

By using the femtosecond angle-resolved spectroscopic imaging technique, the ultrafast buildup dynamics of room-temperature polariton condensation is explicitly visualized in a ZnO whispering gallery mode microcavity. The buildup time of polariton condensation with respect to the arrival of the femtosecond pump pulse decreases with the increasing pump power and reaches a lower limit of about 4 ps. Simulation results by numerically solving the open-dissipative Gross-Pitaevskii equation coupled to an incoherent reservoir are in quantitative agreement with the experimental observations, showing that the scattering from exciton reservoir to the lower polariton branches and the decay from these branches dominate the buildup process.