3,879 research outputs found
Advances in bioprocessing, analytics and formulation of influenza HA-VLP vaccine candidates produced by insect cells
The emergence of new influenza strains demands the continued development of novel, flexible, and scalable platforms for vaccine production. In this study, we describe advancements in the manufacturing process of influenza hemagglutinin (HA)-displaying virus-like particle (VLP)-based vaccines produced by insect cells, from upstream and downstream processing to analytics and formulation.
Aiming to improve influenza HA-VLPs production, evolutionary engineering and process intensification have been applied. Adaptation of stable Sf-9 cells producing HA-VLPs to hypothermic growth resulted in up to 12-fold higher expression. Likewise, adaptation of parental High Five cells to neutral pH induced a 3-fold higher specific HA-VLPs production rate following infection with baculovirus. In both case studies, the adaptation process had no impact on VLPs activity and morphology. Noteworthy, stable adapted Sf-9 cells could be cultured in perfusion (up to 100x106 cell/mL) and continuous (~20x106 cell/mL) operation modes with cell-specific productivity similar to batch mode.
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Elimination of the numerical Cerenkov instability for spectral EM-PIC codes
When using an electromagnetic particle-in-cell (EM-PIC) code to simulate a
relativistically drifting plasma, a violent numerical instability known as the
numerical Cerenkov instability (NCI) occurs. The NCI is due to the unphysical
coupling of electromagnetic waves on a grid to wave-particle resonances,
including aliased resonances, i.e., , where and refer to the time and space
aliases and the plasma is drifting relativistically at velocity in the
-direction. Recent studies have shown that an EM-PIC code which uses a
spectral field solver and a low pass filter can eliminate the fastest growing
modes of the NCI. Based on these studies a new spectral PIC code for studying
laser wakefield acceleration (LWFA) in the Lorentz boosted frame was developed.
However, we show that for parameters of relevance for LWFA simulations in the
boosted frame, a relativistically drifting plasma is susceptible to a host of
additional unstable modes with lower growth rates, and that these modes appear
when the fastest growing unstable modes are filtered out. We show that these
modes are most easily identified as the coupling between modes which are purely
transverse (EM) and purely longitudinal (Langmuir) in the rest frame of the
plasma for specific time and space aliases. We rewrite the dispersion relation
of the drifting plasma for a general field solver and obtain analytic
expressions for the location and growth rate for each unstable mode, i.e, for
each time and space aliased resonances. We show for the spectral solver that
when the fastest growing mode is eliminated a new mode at the fundamental
resonance () can be seen. (Please check the whole abstract in the
paper).Comment: 36 pages, 12 figure
Suspended-core fibers for sensing applications
A brief review on suspended-core fibers for sensing applications is presented. A historical overview over the previous ten years about this special designed microstructure optical fiber is described. This fiber presents attractive optical properties for chemical/biological or gas measurement, but it can be further explored for alternative sensing solutions, namely, in-fiber interferometers based on the suspended-core or suspended-multi-core fiber, for physical parameter monitoring.info:eu-repo/semantics/publishedVersio
Mitigation of numerical Cerenkov radiation and instability using a hybrid finite difference-FFT Maxwell solver and a local charge conserving current deposit
A hybrid Maxwell solver for fully relativistic and electromagnetic (EM)
particle-in-cell (PIC) codes is described. In this solver, the EM fields are
solved in space by performing an FFT in one direction, while using finite
difference operators in the other direction(s). This solver eliminates the
numerical Cerenkov radiation for particles moving in the preferred direction.
Moreover, the numerical Cerenkov instability (NCI) induced by the
relativistically drifting plasma and beam can be eliminated using this hybrid
solver by applying strategies that are similar to those recently developed for
pure FFT solvers. A current correction is applied for the charge conserving
current deposit to correctly account for the EM calculation in hybrid Yee-FFT
solver. A theoretical analysis of the dispersion properties in vacuum and in a
drifting plasma for the hybrid solver is presented, and compared with PIC
simulations with good agreement obtained. This hybrid solver is applied to both
2D and 3D Cartesian and quasi-3D (in which the fields and current are
decomposed into azimuthal harmonics) geometries. Illustrative results for laser
wakefield accelerator simulation in a Lorentz boosted frame using the hybrid
solver in the 2D Cartesian geometry are presented, and compared against results
from 2D UPIC-EMMA simulation which uses a pure spectral Maxwell solver, and
from OSIRIS 2D lab frame simulation using the standard Yee solver. Very good
agreement is obtained which demonstrates the feasibility of using the hybrid
solver for high fidelity simulation of relativistically drifting plasma with no
evidence of the numerical Cerenkov instability
Surface superconductivity in multilayered rhombohedral graphene: Supercurrent
The supercurrent for the surface superconductivity of a flat-band
multilayered rhombohedral graphene is calculated. Despite the absence of
dispersion of the excitation spectrum, the supercurrent is finite. The critical
current is proportional to the zero-temperature superconducting gap, i.e., to
the superconducting critical temperature and to the size of the flat band in
the momentum space
Leafing patterns and drivers across seasonally dry tropical communities
Investigating the timing of key phenological events across environments with variable seasonality is crucial to understand the drivers of ecosystem dynamics. Leaf production in the tropics is mainly constrained by water and light availability. Identifying the factors regulating leaf phenology patterns allows efficiently forecasting of climate change impacts. We conducted a novel phenological monitoring study across four Neotropical vegetation sites using leaf phenology time series obtained from digital repeated photographs (phenocameras). Seasonality differed among sites, from very seasonally dry climate in the caatinga dry scrubland with an eight-month long dry season to the less restrictive Cerrado vegetation with a six-month dry season. To unravel the main drivers of leaf phenology and understand how they influence seasonal dynamics (represented by the green color channel (Gcc) vegetation index), we applied Generalized Additive Mixed Models (GAMMs) to estimate the growing seasons, using water deficit and day length as covariates. Our results indicated that plant-water relationships are more important in the caatinga, while light (measured as day-length) was more relevant in explaining leafing patterns in Cerrado communities. Leafing behaviors and predictor-response relationships (distinct smooth functions) were more variable at the less seasonal Cerrado sites, suggesting that different life-forms (grasses, herbs, shrubs, and trees) are capable of overcoming drought through specific phenological strategies and associated functional traits, such as deep root systems in trees
Travelling colourful patterns in self-organized cellulose-based liquid crystalline structures
Publisher Copyright: © 2021, The Author(s)Cellulose-based systems are useful for many applications. However, the issue of self-organization under non-equilibrium conditions, which is ubiquitous in living matter, has scarcely been addressed in cellulose-based materials. Here, we show that quasi-2D preparations of a lyotropic cellulose-based cholesteric mesophase display travelling colourful patterns, which are generated by a chemical reaction-diffusion mechanism being simultaneous with the evaporation of solvents at the boundaries. These patterns involve spatial and temporal variation in the amplitude and sign of the helix´s pitch. We propose a simple model, based on a reaction-diffusion mechanism, which simulates the observed spatiotemporal colour behaviour.publishersversionpublishe
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