The Application of Model Reactions to the Oxidation of Polyolefins

1972 ◽  
Vol 45 (2) ◽  
pp. 437-449 ◽  
Author(s):  
D. L. Allara ◽  
D. Edelson
Keyword(s):  
Solid Phase ◽  
Repeat Unit ◽  
Fluid Phase ◽  
Amorphous Solid ◽  
Chain Scission ◽  
Computational Techniques ◽  
Low Viscosity ◽  
Chemically Induced ◽  
Alkane Molecule ◽  
Hydrocarbon Polymers

Abstract Initial attempts have been made using computational techniques to apply model compound reactions quantitatively to the oxidation of ethylenepropylene copolymers by molecular oxygen at 100° C. The oxidations of n-butane, isobutane, and isopentane (the simplest model of a polypropylene repeat unit) were chosen as models and applied to the prediction of rates and products in the low conversion oxidations of squalane and a series of ethylenepropylene copolymers of differing composition at 100°. For simplicity, these initial calculations were done for a low viscosity fluid phase. For externally initiated reactions, where calculated and experimental rates (mostly amorphous, solid phase) could be compared, agreement was usually within a factor of 3–5, with the calculated rates generally too fast. Our results on both self- and externally initiated systems suggest that the effect of phase change, from liquid to amorphous solid, on the overall oxidation rate is not large, except in a few cases where effects such as chemically induced crystallization may be significant in the solid phase. Calculations for externally initiated oxidations predict that the rate of chain scission is proportional to the rate of radical production in excellent agreement with experimental results. Our initial results indicate that small alkane molecule reactions can be applied usefully, at present with limited accuracy, to the oxidation of hydrocarbon polymers.

Kinematic and Dynamic Parameters of a Liquid-Solid Pipe Flow Using DPIV∕Accelerometry

2007 ◽  
Vol 129 (11) ◽  
pp. 1415-1421 ◽  
Author(s):  
Joseph Borowsky ◽  
Timothy Wei
Keyword(s):  
Pipe Flow ◽  
Solid Phase ◽  
Fluid Phase ◽  
Central Moment ◽  
Steady Flows ◽  
Dynamic Parameters ◽  
Two Phase ◽  
Turbulence Structures ◽  
Two Phases ◽  
Flat Profile

An experimental investigation of a two-phase pipe flow was undertaken to study kinematic and dynamic parameters of the fluid and solid phases. To accomplish this, a two-color digital particle image velocimetry and accelerometry (DPIV∕DPIA) methodology was used to measure velocity and acceleration fields of the fluid phase and solid phase simultaneously. The simultaneous, two-color DPIV∕DPIA measurements provided information on the changing characteristics of two-phase flow kinematic and dynamic quantities. Analysis of kinematic terms indicated that turbulence was suppressed due to the presence of the solid phase. Dynamic considerations focused on the second and third central moments of temporal acceleration for both phases. For the condition studied, the distribution across the tube of the second central moment of acceleration indicated a higher value for the solid phase than the fluid phase; both phases had increased values near the wall. The third central moment statistic of acceleration showed a variation between the two phases with the fluid phase having an oscillatory-type profile across the tube and the solid phase having a fairly flat profile. The differences in second and third central moment profiles between the two phases are attributed to the inertia of each particle type and its response to turbulence structures. Analysis of acceleration statistics provides another approach to characterize flow fields and gives some insight into the flow structures, even for steady flows.

scholarly journals Low viscosity in the aqueous domain of cell cytoplasm measured by picosecond polarization microfluorimetry.

1991 ◽  
Vol 112 (4) ◽  
pp. 719-725 ◽  
Author(s):  
K Fushimi ◽  
A S Verkman
Keyword(s):  
Free Water ◽  
Fluid Phase ◽  
Rotational Correlation Time ◽  
Cell Cytoplasm ◽  
Intact Cells ◽  
Low Viscosity ◽  
3T3 Fibroblasts ◽  
Anisotropy Decay ◽  
Novel Method ◽  
Swiss 3T3 Fibroblasts

Information about the rheological characteristics of the aqueous cytoplasm can be provided by analysis of the rotational motion of small polar molecules introduced into the cell. To determine fluid-phase cytoplasmic viscosity in intact cells, a polarization microscope was constructed for measurement of picosecond anisotropy decay of fluorescent probes in the cell cytoplasm. We found that the rotational correlation time (tc) of the probes, 2,7-bis-(2-carboxyethyl)-5-(and-6-)carboxyfluorescein (BCECF), 6-carboxyfluorescein, and 8-hydroxypyrene-1,3,6-trisulfonic acid (HPTS) provided a direct measure of fluid-phase cytoplasmic viscosity that was independent of probe binding. In quiescent Swiss 3T3 fibroblasts, tc values were 20-40% longer than those in water, indicating that the fluid-phase cytoplasm is only 1.2-1.4 times as viscous as water. The activation energy of fluid-phase cytoplasmic viscosity was 4 kcal/mol, which is similar to that of water. Fluid-phase cytoplasmic viscosity was altered by less than 10% upon addition of sucrose to decrease cell volume, cytochalasin B to disrupt cell cytoskeleton, and vasopressin to activate phospholipase C. Nucleoplasmic and peripheral cytoplasmic viscosities were not different. Our results establish a novel method to measure fluid-phase cytoplasmic viscosity, and indicate that fluid-phase cytoplasmic viscosity in fibroblasts is similar to that of free water.

scholarly journals Predicting the glass transition temperature and viscosity of secondary organic material using molecular composition

2018 ◽  
Vol 18 (9) ◽  
pp. 6331-6351 ◽  
Author(s):  
Wing-Sy Wong DeRieux ◽  
Ying Li ◽  
Peng Lin ◽  
Julia Laskin ◽  
Alexander Laskin ◽  
...  
Keyword(s):  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Chemical Composition ◽  
Organic Compounds ◽  
Molar Mass ◽  
Solid Phase ◽  
Amorphous Solid ◽  
Semi Solid ◽  
Oxygen Atoms

Abstract. Secondary organic aerosol (SOA) accounts for a large fraction of submicron particles in the atmosphere. SOA can occur in amorphous solid or semi-solid phase states depending on chemical composition, relative humidity (RH), and temperature. The phase transition between amorphous solid and semi-solid states occurs at the glass transition temperature (Tg). We have recently developed a method to estimate Tg of pure compounds containing carbon, hydrogen, and oxygen atoms (CHO compounds) with molar mass less than 450 g mol−1 based on their molar mass and atomic O : C ratio. In this study, we refine and extend this method for CH and CHO compounds with molar mass up to ∼ 1100 g mol−1 using the number of carbon, hydrogen, and oxygen atoms. We predict viscosity from the Tg-scaled Arrhenius plot of fragility (viscosity vs. Tg∕T) as a function of the fragility parameter D. We compiled D values of organic compounds from the literature and found that D approaches a lower limit of ∼ 10 (±1.7) as the molar mass increases. We estimated the viscosity of α-pinene and isoprene SOA as a function of RH by accounting for the hygroscopic growth of SOA and applying the Gordon–Taylor mixing rule, reproducing previously published experimental measurements very well. Sensitivity studies were conducted to evaluate impacts of Tg, D, the hygroscopicity parameter (κ), and the Gordon–Taylor constant on viscosity predictions. The viscosity of toluene SOA was predicted using the elemental composition obtained by high-resolution mass spectrometry (HRMS), resulting in a good agreement with the measured viscosity. We also estimated the viscosity of biomass burning particles using the chemical composition measured by HRMS with two different ionization techniques: electrospray ionization (ESI) and atmospheric pressure photoionization (APPI). Due to differences in detected organic compounds and signal intensity, predicted viscosities at low RH based on ESI and APPI measurements differ by 2–5 orders of magnitude. Complementary measurements of viscosity and chemical composition are desired to further constrain RH-dependent viscosity in future studies.

scholarly journals Determination of Phase-Eigenvalues by Rational Factorization and Enhanced Simulation of Two-Phase Mass Flow

2019 ◽  
Vol 2 (2) ◽  
pp. 61-77
Author(s):  
Puskar R. Pokhrel ◽  
Bhadra Man Tuladhar
Keyword(s):  
Fluid Dynamics ◽  
Debris Flows ◽  
Lateral Pressure ◽  
Solid Phase ◽  
Fluid Phase ◽  
Factorization Method ◽  
Phase Interaction ◽  
Two Phase ◽  
Simulation Results

In this paper, we present simple and exact eigenvalues for both the solid- and fluid-phases of the real two-phase general model developed by Pudasaini (2012); we call these phase-eigenvalues, the solid- phase-eigenvalues and the fluid-phase-eigenvalues. Results are compared by applying the derived phase- eigenvalues that incorporate the phase-interactions in the two-phase debris movements against the simple and classical solid and fluid eigenvalues without any phase interaction. We have constructed several different set of eigenvalues including the coupled phase eigenvalues by using rational factorization method. At first, we consider for general debris height; factorizing the solid and fluid lateral pressure contributions by considering the negligible pressure gradient; negligible solid lateral pressure; negligible fluid lateral pressure; negligible solid and fluid lateral pressure. Secondly, for a thin debris ow height, we also construct the fourth set of eigenvalues in three different cases. These phase-eigenvalues incorporate strong interaction between the solid and fluid dynamics. The simulation results are produced by taking all these different sets of coupled phase-eigenvalues and are compared with the classical uncoupled set of solid and fluid eigenvalues. The results indicate the importance of phase-eigenvalues and supports for a complete description of the phase- eigenvalues for the enhanced description of real two-phase debris flows and landslide motions.

scholarly journals Critical energy landscape of linear soft spheres

2020 ◽  
Vol 9 (1) ◽  
Author(s):  
Silvio Franz ◽  
Antonio Sclocchi ◽  
Pierfrancesco Urbani
Keyword(s):  
Critical Exponents ◽  
Solid Phase ◽  
Energy Landscape ◽  
Amorphous Solid ◽  
Critical Energy ◽  
Contact Network ◽  
Stable States ◽  
Potential Energy Landscape ◽  
Soft Spheres ◽  
Non Linear System

We show that soft spheres interacting with a linear ramp potential when overcompressed beyond the jamming point fall in an amorphous solid phase which is critical, mechanically marginally stable and share many features with the jamming point itself. In the whole phase, the relevant local minima of the potential energy landscape display an isostatic contact network of perfectly touching spheres whose statistics is controlled by an infinite lengthscale. Excitations around such energy minima are non-linear, system spanning, and characterized by a set of non-trivial critical exponents. We perform numerical simulations to measure their values and show that, while they coincide, within numerical precision, with the critical exponents appearing at jamming, the nature of the corresponding excitations is richer. Therefore, linear soft spheres appear as a novel class of finite dimensional systems that self-organize into new, critical, marginally stable, states.

scholarly journals Heterogeneous ice nucleation of viscous secondary organic aerosol produced from ozonolysis of <i>α</i>-pinene

2016 ◽  
Vol 16 (10) ◽  
pp. 6495-6509 ◽  
Author(s):  
Karoliina Ignatius ◽  
Thomas B. Kristensen ◽  
Emma Järvinen ◽  
Leonid Nichman ◽  
Claudia Fuchs ◽  
...  
Keyword(s):  
Secondary Organic Aerosol ◽  
Solid Phase ◽  
Particle Surface ◽  
Amorphous Solid ◽  
Organic Aerosol ◽  
Ice Nucleation ◽  
Cloud Formation ◽  
Particle Surface Area ◽  
Semi Solid ◽  
Heterogeneous Ice Nucleation

Abstract. There are strong indications that particles containing secondary organic aerosol (SOA) exhibit amorphous solid or semi-solid phase states in the atmosphere. This may facilitate heterogeneous ice nucleation and thus influence cloud properties. However, experimental ice nucleation studies of biogenic SOA are scarce. Here, we investigated the ice nucleation ability of viscous SOA particles. The SOA particles were produced from the ozone initiated oxidation of α-pinene in an aerosol chamber at temperatures in the range from −38 to −10 °C at 5–15 % relative humidity with respect to water to ensure their formation in a highly viscous phase state, i.e. semi-solid or glassy. The ice nucleation ability of SOA particles with different sizes was investigated with a new continuous flow diffusion chamber. For the first time, we observed heterogeneous ice nucleation of viscous α-pinene SOA for ice saturation ratios between 1.3 and 1.4 significantly below the homogeneous freezing limit. The maximum frozen fractions found at temperatures between −39.0 and −37.2 °C ranged from 6 to 20 % and did not depend on the particle surface area. Global modelling of monoterpene SOA particles suggests that viscous biogenic SOA particles are indeed present in regions where cirrus cloud formation takes place. Hence, they could make up an important contribution to the global ice nucleating particle budget.

Thermal Analysis of Multijet Impingement Through Porous Media to Design a Confined Heat Management System

2019 ◽  
Vol 141 (8) ◽  
Author(s):  
Carlos Zing ◽  
Shadi Mahjoob
Keyword(s):  
Porous Media ◽  
High Efficiency ◽  
Solid Phase ◽  
Electronics Cooling ◽  
Jet Impingement ◽  
Fluid Phase ◽  
Volume Averaging ◽  
High Heat Flux ◽  
Base Temperature ◽  
Heat Management

Thermal management has a key role in the development of advanced electronic devices to keep the device temperature below a maximum operating temperature. Jet impingement and high conductive porous inserts can provide a high efficiency cooling and temperature control for a variety of applications including electronics cooling. In this work, advanced heat management devices are designed and numerically studied employing single and multijet impingement through porous-filled channels with inclined walls. The base of these porous-filled nonuniform heat exchanging channels will be in contact with the devices to be cooled; as such the base is subject to a high heat flux leaving the devices. The coolant enters the heat exchanging device through single or multijet impingement normal to the base, moves through the porous field and leaves through horizontal exit channels. For numerical modeling, local thermal nonequilibrium model in porous media is employed in which volume averaging over each of the solid and fluid phase results in two energy equations, one for solid phase and one for fluid phase. The cooling performance of more than 30 single and multijet impingement designs are analyzed and compared to achieve advantageous designs with low or uniform base temperature profiles and high thermal effectiveness. The effects of porosity value and employment of 5% titanium dioxide (TiO2) in water in multijet impingement cases are also investigated.

The Scission of Polysulfide Crosslinks in Scrap Rubber Particles through Phase Transfer Catalysis

1982 ◽  
Vol 55 (5) ◽  
pp. 1499-1515 ◽  
Author(s):  
Paul P. Nicholas
Keyword(s):  
Phase Transfer ◽  
Alkylating Agents ◽  
Decomposition Reaction ◽  
Chain Scission ◽  
Model Studies ◽  
Low Viscosity ◽  
Diffusion Controlled ◽  
Onium Salts ◽  
Rubber Particles ◽  
Rate Behavior

Abstract Hydroxide ions transported by onium ions from water into swollen rubber particles rapidly break polysulfide crosslinks with little or no main chain scission. However, methylated monosulfide crosslinks do not cleave under these conditions. The reaction is not truly catalytic because the quaternary ammonium is decomposed. Model studies with N-methyl-N,N,N-tri-n-alkylammonium chlorides and di-2-cyclohexen-1-yl disulfide show that the decomposition reaction involves a highly selective methylation of the thiolate intermediate. However, catalyst decomposition can be inhibited with added alkylating agents. Alkylating agents also improve catalyst efficiency during devulcanization. The Hofmann reaction is yet another route for catalyst decomposition, but the rate is too slow to be competitive. Several onium salts have been examined in this process. In general, those having several large alkyl substituents are the better performers, consistent with the known partitioning/reaction rate behavior of such catalysts in simple, low viscosity solvents. However, with N-methyl-N,N,N-tri-n-alkylammonium chlorides, the rate decreases as the tri-n-alkyl substituents become very large, e.g., C18H37. This may originate from a slow, diffusion-controlled reaction that is peculiar to the network structure of the swollen vulcanizate.

scholarly journals Arm lymphedema after treatment of breast cancer: Etiology, diagnosis, and management

2015 ◽  
Vol 01 (02) ◽  
pp. 077-083 ◽  
Author(s):  
Ashish Goel ◽  
Juhi Agarwal ◽  
Sandeep Mehta ◽  
Kapil Kumar
Keyword(s):  
Breast Cancer ◽  
Solid Phase ◽  
Subcutaneous Tissue ◽  
Fluid Phase ◽  
Team Work ◽  
Treatment Modalities ◽  
Cancer Etiology ◽  
Complete Decongestive Therapy ◽  
Arm Lymphedema ◽  
Decongestive Therapy

ABSTRACTBreast cancer related lymphedema (BCRL) is a chronic debilitating condition seen after treatment of breast cancer. The overall incidence varies from 20% to 56% in all patients treated for breast cancer. Every patient is at a lifelong risk for BCRL and the risk goes on increasing as the followup period increases. Locoregional treatment including surgery or radiotherapy is the most common risk factor for development of arm lymphedema. There are two phases of arm lymphedema. There is increased fluid accumulation in the fluid phase of lymphedema which later on goes into the solid phase where fat and fibrotic tissue is deposited in the subcutaneous tissue. The treatment of BCRL is a challenge both for the patient and the treating surgeon and it needs multidisciplinary team work to be successful. Non-surgical treatment modalities include complete decongestive therapy (CDT) and pneumatic compression therapy. Surgery for BCRL is usually undertaken as a salvage modality after failure of conservative approaches. The surgical spectrum for BCRL varies from extensive excisional operations which were commonly done in the past to newer methods like suction assisted protein lipectomy, lymphatic reconstruction and vascular lymph node transfer (VLNT) using super-microsurgical techniques. There is no consensus regarding the preference of one procedure over other due to lack of randomised control trials. It is however suggested to do lymphovenous anastomosis and complete decongestive therapy for early cases in fluid phase; while patients in the solid phase may be treated with a combination of liposuction with CDT or VLNT alone.

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