scholarly journals Enhanced diffusion by reversible binding to active polymers

2021 ◽  
Author(s):  
Shankar Lalitha Sridhar ◽  
Jeffrey Dunagin ◽  
Kanghyeon Koo ◽  
Loren Hough ◽  
Franck J Vernerey
Keyword(s):  
Relative Length ◽  
Synthetic Polymers ◽  
Diffusive Transport ◽  
Optimum Conditions ◽  
Reversible Binding ◽  
Macromolecular Transport ◽  
Enhanced Diffusion ◽  
Mechanics Model ◽  
Random Forces ◽  
Insight Into

Cells are known to use reversible binding to active biopolymer networks to allow diffusive transport of particles in an otherwise impenetrable mesh. We here determine the motion of a particle that experiences random forces during binding and unbinding events while being constrained by attached polymers. Using Monte-Carlo simulations and a statistical mechanics model, we find that enhanced diffusion is possible with active polymers. However, this is possible only under optimum conditions that has to do with the relative length of the chains to that of the plate. For example, in systems where the plate is shorter than the chains, diffusion is maximum when many chains have the potential to bind but few remain bound at any one time. Interestingly, if the chains are shorter than the plate, we find that diffusion is maximized when more active chains remain transiently bound. The model provides insight into these findings by elucidating the mechanisms for binding-mediated diffusion in biology and design rules for macromolecular transport in transient synthetic polymers.

An Insight into the Polymeric Nanoparticles Applications in Diabetes Diagnosis and Treatment

2021 ◽  
Vol 21 ◽  
Author(s):  
Parisa Dehghani ◽  
Monireh Esameili Rad ◽  
Atefeh Zarepour ◽  
Ponnurengam Malliappan Sivakumar ◽  
Ali Zarrabi
Keyword(s):  
Polymeric Nanoparticles ◽  
Synthetic Polymers ◽  
Diagnostic Methods ◽  
Diagnosis And Treatment ◽  
Diabetes Diagnosis ◽  
Transport Mechanisms ◽  
Different Types ◽  
Treatment And Diagnosis ◽  
Insight Into

: Diabetes mellitus (DM) is a type of chronic metabolic disease that has affected millions of people worldwide and is known with a defect in the amount of insulin secretion, insulin functions, or both. This deficiency leads to an increase in the amounts of glucose, which could be accompanied by long-term damages to other organs such as eyes, kidneys, heart, and nervous system. Thus, introducing an appropriate approach for diagnosis and treatment of different types of DM is the aim of several researches. By the emergence of nanotechnology and its application in medicine, new approaches were presented for these purposes. The object of this review article is to introduce different types of polymeric nanoparticles (PNPs), as one of the most important classes of nanoparticles, for diabetic management. To achieve this goal, at first, some of the conventional therapeutic and diagnostic methods of DM will be reviewed. Then, different types of PNPs, in two forms of natural and synthetic polymers with different properties, as a new method for DM treatment and diagnosis will be introduced. In the next section, the transport mechanisms of these types of nano-carriers across the epithelium, via paracellular and transcellular pathways will be explained. Finally, the clinical use of PNPs in the treatment and diagnosis of DM will be summarized. Based on the results of this literature review, PNPs could be considered one of the most promising methods for DM management.

Transport in Pulsatile Axisymmetric Stented Arterial Models From Location-Dependent Variations in Permeability and Mechanical Properties

2011 ◽  
Author(s):  
Joseph T. Keyes ◽  
Bruce R. Simon ◽  
Jonathan P. Vande Geest
Keyword(s):  
Mechanical Properties ◽  
Drug Delivery ◽  
Relative Influence ◽  
Drug Eluting Stents ◽  
Diffusive Transport ◽  
Antiproliferative Effects ◽  
Drug Eluting ◽  
Tissue System ◽  
Localized Drug Delivery ◽  
Insight Into

Drug-eluting stents (DESs) perform their antiproliferative effects through the use of localized drug delivery. The delivery may be computationally modeled to determine efficacy of the DES-tissue system and utilizes coupled convective and diffusive transport. Since the movement of solutes through the wall is via the coupled effects of convective and diffusive transport, the relative influence of these factors provides insight into the governing forces of localized DES drug delivery [1].

Optimum Conditions for the Operation of Airline Aircraft

1953 ◽  
Vol 57 (512) ◽  
pp. 524-527 ◽  
Author(s):  
Alan H. Stratford
Keyword(s):  
Conventional Method ◽  
Direct Costs ◽  
Profit Margin ◽  
Optimum Conditions ◽  
Transport Aircraft ◽  
The Subject ◽  
Aircraft Type ◽  
The Individual ◽  
Insight Into

The Conventional method of assessing the direct costs or the aircraft type costs on a passenger mile or ton mile basis does not necessarily give a sufficient indication of the economic merit of a particular type of transport aircraft. It can be misleading when comparing aircraft of widely different design, and it does not indicate the best routes for effective airline exploitation.The profit margin in relation to the fundamental cost or investment unit of the individual airline must be the ultimate yardstick of transport aircraft selection and this is here analysed with a view to providing further insight into the optimum conditions for potential profits. This study of the subject draws attention to the primary factors involved and suggests a criterion which can be simplified into a form valid for most airline economies.

scholarly journals The cryo-EM structure of a 12-subunit variant of RNA polymerase I reveals dissociation of the A49-A34.5 heterodimer and rearrangement of subunit A12.2

eLife ◽  
2019 ◽  
Vol 8 ◽  
Author(s):  
Lucas Tafur ◽  
Yashar Sadian ◽  
Jonas Hanske ◽  
Rene Wetzel ◽  
Felix Weis ◽  
...  
Keyword(s):  
Rna Polymerase ◽  
Ribosomal Rna ◽  
Transcription Initiation ◽  
Molecular Mechanisms ◽  
Reversible Binding ◽  
Cryo Electron Microscopy ◽  
Nucleotide Analog ◽  
Pol I ◽  
Polymerase I ◽  
Insight Into

RNA polymerase (Pol) I is a 14-subunit enzyme that solely transcribes pre-ribosomal RNA. Cryo-electron microscopy (EM) structures of Pol I initiation and elongation complexes have given first insights into the molecular mechanisms of Pol I transcription. Here, we present cryo-EM structures of yeast Pol I elongation complexes (ECs) bound to the nucleotide analog GMPCPP at 3.2 to 3.4 Å resolution that provide additional insight into the functional interplay between the Pol I-specific transcription-like factors A49-A34.5 and A12.2. Strikingly, most of the nucleotide-bound ECs lack the A49-A34.5 heterodimer and adopt a Pol II-like conformation, in which the A12.2 C-terminal domain is bound in a previously unobserved position at the A135 surface. Our structural and biochemical data suggest a mechanism where reversible binding of the A49-A34.5 heterodimer could contribute to the regulation of Pol I transcription initiation and elongation.

Simulation of softening in high pressure torsion process using continuum damage mechanics model

2021 ◽  
pp. 095440622110338
Author(s):  
Shubhi Katiyar ◽  
Prakash Mahadeo Dixit
Keyword(s):  
High Pressure ◽  
Damage Mechanics ◽  
High Pressure Torsion ◽  
Compressive Load ◽  
Continuum Damage Mechanics ◽  
Material Model ◽  
Work Piece ◽  
Continuum Damage ◽  
Mechanics Model ◽  
Insight Into

Severe Plastic Deformations (SPD) processes are used for grain refinement without any loss in ductility. Among various SPD processes, High Pressure Torsion (HPT) is extensively used in industries due to generation of high angle grain boundaries and cost effectiveness. Very little work has been reported on the numerical analysis of softening with recovery that might occur in a work-piece undergoing HPT. The present work is an attempt to study the softening behaviour in HPT processed mild steel and aluminium alloy using the Lemaitre’s continuum damage mechanics (CDM) model. This model is implemented in ABAQUS/Explicit through a user defined material model subroutine (VUMAT). A parametric study is carried out to study the effect on softening of various parameters like the compressive load, the friction at the die-workpiece interface, and the height to diameter ratio. Information about the softening with recovery provides an insight into the hardness and microstructure homogeneity in HPT processed work-piece, which is useful in the design of HPT process.

scholarly journals Heterogeneity formation within biofilm systems

2018 ◽  
Vol 29 (6) ◽  
pp. 1020-1034 ◽  
Author(s):  
ANDREAS C. ARISTOTELOUS ◽  
YURY GRABOVSKY ◽  
ISAAC KLAPPER
Keyword(s):  
Linear Analysis ◽  
Length Scale ◽  
Diffusive Transport ◽  
Full Model ◽  
Transport Efficiency ◽  
Community Function ◽  
Functional Consequences ◽  
Scale Properties ◽  
Insight Into ◽  
Structural Heterogeneities

Biofilms, and collections of embedded microbial communities, present structural heterogeneities with functional consequences for important processes, such as transport. The origin of such structures has been unclear. Here, we propose that they can arise as a consequence of diffusive transport limitation. To illustrate, a model allowing internal heterogeneity is developed. Linear analysis is applied to a simplified version of the model suggesting that heterogeneity forms on (or below) the active layer length, a length scale that may not be suitable for homogenization, with non-trivial implications for system scale properties such as reduction in system-wide diffusive transport efficiency. Numerics suggest that the simplified model provides useful insight into behaviour of the full model. We then show examples based on microcolony formation in host domains and argue that internal heterogeneity can be related to community function.

scholarly journals Investigation of Co3O4 and LaCoO3 Interaction by Performing N2O Decomposition Tests under Co3O4-CoO Transition Temperature

Catalysts ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 325
Author(s):  
Ewa M. Iwanek (nee Wilczkowska) ◽  
Leonarda F. Liotta ◽  
Giuseppe Pantaleo ◽  
Krzysztof Krawczyk ◽  
Ewa Gdyra ◽  
...  
Keyword(s):  
Cobalt Oxide ◽  
Cobalt Catalyst ◽  
N2o Decomposition ◽  
Oxygen Scavenger ◽  
Oxygen Desorption ◽  
Enhanced Diffusion ◽  
Beneficial Effects ◽  
Two Phases ◽  
Positive Effect ◽  
Insight Into

The research presented in this paper addresses the question: How does the addition of a small amount of LaCoO3 impact the activity of a Co3O4 catalyst? By testing such a catalyst in N2O decomposition under conditions at which the thermal decomposition of Co3O4 to CoO is possible, one gains unique insight into how the two phases interact. The activity of such a catalyst increases in the entire studied temperature range, unlike the activity of the undoped cobalt catalyst which is lower at 850 °C than at 800 °C due to the reduction of Co3O4 to CoO. XRD measurements showed that CoO was also the main cobalt oxide present in the Co3.5La catalyst after operating at 850 °C, as did the XPS measurements, but there was no drop of activity associated with this change. The influence of NO, O2 and H2O on the activity of the new catalyst, Co3.5La, was determined. Lack of positive effect of NO, a known oxygen scavenger, on the activity was noticed at all temperatures, showing that the effect of LaCoO3 is probably due to increased oxygen desorption. Temperature programed oxidation (TPO) tests showed that the beneficial effects of the presence of LaCoO3 on the activity of cobalt oxide at 850 °C were probably caused by enhanced diffusion of O2− anions through the entire catalyst, which facilitates desorption of oxygen molecules from the surface.

scholarly journals AN INSIGHT INTO THE ROLE OF BIOMASS, BIOCOMPOUNDS AND SYNTHETIC POLYMERS AS ADDITIVES TO COAL FOR THE SYNTHESIS OF CARBON FOAMS

2021 ◽  
pp. 105359
Author(s):  
E. Rodríguez ◽  
M.A. Diez ◽  
C. Antuña-Nieto ◽  
M.A. López-Antón ◽  
R. García ◽  
...  
Keyword(s):  
Synthetic Polymers ◽  
Carbon Foams ◽  
Insight Into

On the Influence of Boron-Interstitial Complexes on Transient Enhanced Diffusion

1999 ◽  
Vol 568 ◽  
Author(s):  
D. Stiebel ◽  
P. Pichler ◽  
H. Ryssel
Keyword(s):  
Ion Implantation ◽  
Experimental Results ◽  
Enhanced Diffusion ◽  
Transient Enhanced Diffusion ◽  
Dopant Atoms ◽  
Insight Into

ABSTRACTWe present new experimental results on the transient enhanced diffusion (TED) of boron after ion implantation. The investigation is focussed on effects that influence TED of shallow profiles in the absence of {311}-defects. Under these conditions, TED is mainly determined by the formation of boron-interstitial complexes (BIC). In addition, effects from the proximity of the surface become more and more important. Insight into the behavior of the dopant atoms is obtained by the comparison with simulations.

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