Synthesis, Characterization, and Dynamics of a Rod/Sphere Organoceramic Composite Liquid

1992 ◽  
Vol 274 ◽  
Author(s):  
Mark A. Tracy ◽  
R. Pecora
Keyword(s):  
Experimental Studies ◽  
Liquid System ◽  
Organic Coating ◽  
Molecular Weights ◽  
Naturally Occurring ◽  
Wide Range ◽  
Molecular Composites ◽  
Ceramic Precursors ◽  
Rigid Rod ◽  
System 1

ABSTRACTComposite liquids – liquids composed of polymers, particles, and small molecule solvents – constitute an important class of synthetic and naturally occurring materials. Examples include molecular composites, ceramic precursors, lubricants, adhesives, and the cytoplasm in biological cells. Due to the complexity of these liquids, experimental studies of precisely defined systems are essential in developing an understanding of the interactions between all components in the liquid. Unfortunately, such fundamental studies have been relatively rare due to both the difficulty of synthesizing precisely defined composite liquids and the lack of adequate experimental methods to monitor the motions of the various constituents.We have recently reported the synthesis, characterization and some studies of the dynamics of a rod/sphere composite liquid system [1]. In our case the “polymer” constituent is a rigid rod polymer, poly(γ-benzyl-α,L-glutamate) (PBLG). Rigid rod polymers are frequently used in composite liquids as viscosity enhancers. PBLG is commercially available in a wide range of molecular weights and its static and dynamic behavior in dilute and nondilute solutions has been studied. It, in addition, forms mesophases in the concentrated regime. The ceramic “particles” in our composite liquid are coated silica spheres. These spheres are synthesized by the method of Stober et. al. [2] and coated with an organic coating (3-(trimethoxysilyl)propyl methacrylate (TPM)) following a procedure based on that of Philipse et. al. [3] to render them dispersible in organic solvents. The spheres with sizes in the range from 10 nm up to almost 1μm can be synthesized with a relatively narrow size distribution. The solvent in our studies is dimethylformamide (DMF). Both polymer and particle are dispersible as singlets (nonaggregating) in these solvents and the PBLG retains its rigid (or nearly rigid) rod conformation. The diffusion of both the polymer and the sphere in the composite liquid is measured by dynamic light scattering (DLS) [4]. In this paper, we focus on the spheres and examine the effects of rod concentration and rod length on the diffusion of different size spheres. This study suggests that the solution microstructure has an important influence on sphere diffusion.

scholarly journals Studies on Underwater Electric Discharge and Associated Pressure Waves

2021 ◽  
Author(s):  
Valeriy Chernyak ◽  
Vitalii Iukhymenko ◽  
Evgen Martysh ◽  
Oleg Nedybaliuk ◽  
Oleg Fedorovich ◽  
...  
Keyword(s):  
Shock Wave ◽  
Shock Waves ◽  
Experimental Studies ◽  
Liquid System ◽  
Storage Capacitor ◽  
Electric Discharges ◽  
Cylindrical Plasma ◽  
Reflected Shock ◽  
Converging Shock Waves ◽  
Wide Range

<p>Pulsed electric discharges in a liquid with the sufficiently wide range of energy contributions to them can generate diverging shock waves. А significant part of this energy is carried away by these waves from the center of the system to its periphery. At the same time, pulsed plasma-liquid systems limited by reflecting walls of both cylindrical and spherical geometry are insufficiently studied. A fundamental feature of such systems is the generation of a sequence of both diverging and converging (reflected) shock waves by a single pulse discharge. It was shown earlier that in a cylindrical plasma-liquid system with a height of the cylinder (h) comparable with the interelectrode distance (d), radius of the cylinder base R (at R >> h), when discharge current is increased, the ratio of the second diverging shock wave amplitude to the amplitude of the first diverging shock wave can be → 1. This leads to effective return of the energy carried away to the periphery back to the center of the system by converging shock waves. The collapse of the converging shock waves and initiated processes in the center of such plasma-fluid systems can be very interesting. The paper presents the results of experimental studies of pulsed cylindrical plasma-liquid system using both H<sub>2</sub>O and a mixture of H<sub>2</sub>O / D<sub>2</sub>O and pure D<sub>2</sub>O as a liquid. The energy-storage capacitor is charged by using a high voltage DC power supply (up to 70 kV).</p>

Thermomechanical Characterization of the Molecular Weight of Linear Polymers Exemplified by Natural Rubber

1964 ◽  
Vol 37 (1) ◽  
pp. 99-102
Author(s):  
B. Ya Teitelbaum ◽  
K. F. Gubanov
Keyword(s):  
Molecular Weight ◽  
Experimental Studies ◽  
Thermomechanical Properties ◽  
Linear Polymers ◽  
Molecular Weights ◽  
Calculated Molecular Weight ◽  
Low Degree ◽  
Wide Range ◽  
High Elasticity

Abstract In the previous work of Kargin and Slonimskii and that of Kargin and Sogolov who studied the behavior of polymers over a wide range of temperature, it was shown that the shape of thermomechanical curves depends on magnitude of molecular weight of the polymers. As a result of investigation of theory and actual experimental studies in which polyisobutylene was employed, it was demonstrated that molecular weight could be estimated on the basis of thermomechanical properties. This suggested a relationship between the magnitude of molecular weight M found from the thermomechanical curves and that which was determined from glass temperatures Tg and fluid temperatures Tf. For practical use of this relationship, it is necessary to know the magnitude of the segments and two empirical constants. These values can be found by calculation of molecular weights of three different fractions of the polymer. This can be accomplished experimentally by any independent method. Once these magnitudes are determined, it is necessary to find, by means of the thermomechanical curve, the values Tg and Tf, in order to calculate the molecular weight of any sample of the same polymer. Because of the low degree of accuracy of determination of these values, and because of the peculiar differences, the reliability of the calculated molecular weight cannot be great, especially since the equation utilizes the logarithm of the molecular weight figure and not the molecular weight itself. Apparently the graphic solution is simpler than analytical methods: by means of the data of thermomechanical studies for various fractions of known molecular weights it is possible to graph the dependence of M or log Mon Tf−Tg. From what has been said, it is evident that we may use the demonstrated method only for polymers of high elasticity, and furthermore, only for those fractions in which Tf−Tg is greater than zero.

scholarly journals Studies on Underwater Electric Discharge and Associated Pressure Waves

2021 ◽  
Author(s):  
Valeriy Chernyak ◽  
Vitalii Iukhymenko ◽  
Evgen Martysh ◽  
Oleg Nedybaliuk ◽  
Oleg Fedorovich ◽  
...  
Keyword(s):  
Shock Wave ◽  
Shock Waves ◽  
Experimental Studies ◽  
Liquid System ◽  
Storage Capacitor ◽  
Electric Discharges ◽  
Cylindrical Plasma ◽  
Reflected Shock ◽  
Converging Shock Waves ◽  
Wide Range

<p>Pulsed electric discharges in a liquid with the sufficiently wide range of energy contributions to them can generate diverging shock waves. А significant part of this energy is carried away by these waves from the center of the system to its periphery. At the same time, pulsed plasma-liquid systems limited by reflecting walls of both cylindrical and spherical geometry are insufficiently studied. A fundamental feature of such systems is the generation of a sequence of both diverging and converging (reflected) shock waves by a single pulse discharge. It was shown earlier that in a cylindrical plasma-liquid system with a height of the cylinder (h) comparable with the interelectrode distance (d), radius of the cylinder base R (at R >> h), when discharge current is increased, the ratio of the second diverging shock wave amplitude to the amplitude of the first diverging shock wave can be → 1. This leads to effective return of the energy carried away to the periphery back to the center of the system by converging shock waves. The collapse of the converging shock waves and initiated processes in the center of such plasma-fluid systems can be very interesting. The paper presents the results of experimental studies of pulsed cylindrical plasma-liquid system using both H<sub>2</sub>O and a mixture of H<sub>2</sub>O / D<sub>2</sub>O and pure D<sub>2</sub>O as a liquid. The energy-storage capacitor is charged by using a high voltage DC power supply (up to 70 kV).</p>

Morphology of High-Performance Rigid-Rod Polymer Fibers and Molecular Composites

1989 ◽  
Vol 47 ◽  
pp. 338-339
Author(s):  
W.W. Adams ◽  
S. J. Krause
Keyword(s):  
Tensile Strength ◽  
High Performance ◽  
Liquid Crystalline ◽  
Molecular Level ◽  
Synergistic Effects ◽  
Tensile Modulus ◽  
Commercial Development ◽  
The Matrix ◽  
Molecular Composites ◽  
Rigid Rod

Rigid-rod polymers such as PBO, poly(paraphenylene benzobisoxazole), Figure 1a, are now in commercial development for use as high-performance fibers and for reinforcement at the molecular level in molecular composites. Spinning of liquid crystalline polyphosphoric acid solutions of PBO, followed by washing, drying, and tension heat treatment produces fibers which have the following properties: density of 1.59 g/cm3; tensile strength of 820 kpsi; tensile modulus of 52 Mpsi; compressive strength of 50 kpsi; they are electrically insulating; they do not absorb moisture; and they are insensitive to radiation, including ultraviolet. Since the chain modulus of PBO is estimated to be 730 GPa, the high stiffness also affords the opportunity to reinforce a flexible coil polymer at the molecular level, in analogy to a chopped fiber reinforced composite. The objectives of the molecular composite concept are to eliminate the thermal expansion coefficient mismatch between the fiber and the matrix, as occurs in conventional composites, to eliminate the interface between the fiber and the matrix, and, hopefully, to obtain synergistic effects from the exceptional stiffness of the rigid-rod molecule. These expectations have been confirmed in the case of blending rigid-rod PBZT, poly(paraphenylene benzobisthiazole), Figure 1b, with stiff-chain ABPBI, poly 2,5(6) benzimidazole, Fig. 1c A film with 30% PBZT/70% ABPBI had tensile strength 190 kpsi and tensile modulus of 13 Mpsi when solution spun from a 3% methane sulfonic acid solution into a film. The modulus, as predicted by rule of mixtures, for a film with this composition and with planar isotropic orientation, should be 16 Mpsi. The experimental value is 80% of the theoretical value indicating that the concept of a molecular composite is valid.

scholarly journals Image Statistics Preserving Encrypt-then-Compress Scheme Dedicated for JPEG Compression Standard

Entropy ◽  
2021 ◽  
Vol 23 (4) ◽  
pp. 421
Author(s):  
Dariusz Puchala ◽  
Kamil Stokfiszewski ◽  
Mykhaylo Yatsymirskyy
Keyword(s):  
Statistical Analysis ◽  
Image Encryption ◽  
Experimental Studies ◽  
Quality Measures ◽  
Input Image ◽  
Jpeg Compression ◽  
Image Statistics ◽  
Compression Stage ◽  
Wide Range ◽  
The Impact

In this paper, the authors analyze in more details an image encryption scheme, proposed by the authors in their earlier work, which preserves input image statistics and can be used in connection with the JPEG compression standard. The image encryption process takes advantage of fast linear transforms parametrized with private keys and is carried out prior to the compression stage in a way that does not alter those statistical characteristics of the input image that are crucial from the point of view of the subsequent compression. This feature makes the encryption process transparent to the compression stage and enables the JPEG algorithm to maintain its full compression capabilities even though it operates on the encrypted image data. The main advantage of the considered approach is the fact that the JPEG algorithm can be used without any modifications as a part of the encrypt-then-compress image processing framework. The paper includes a detailed mathematical model of the examined scheme allowing for theoretical analysis of the impact of the image encryption step on the effectiveness of the compression process. The combinatorial and statistical analysis of the encryption process is also included and it allows to evaluate its cryptographic strength. In addition, the paper considers several practical use-case scenarios with different characteristics of the compression and encryption stages. The final part of the paper contains the additional results of the experimental studies regarding general effectiveness of the presented scheme. The results show that for a wide range of compression ratios the considered scheme performs comparably to the JPEG algorithm alone, that is, without the encryption stage, in terms of the quality measures of reconstructed images. Moreover, the results of statistical analysis as well as those obtained with generally approved quality measures of image cryptographic systems, prove high strength and efficiency of the scheme’s encryption stage.

scholarly journals Modes of Interaction in Naturally Occurring Medical Encounters With General Practitioners: The “One in a Million” Study

2021 ◽  
pp. 104973232199379
Author(s):  
Olaug S. Lian ◽  
Sarah Nettleton ◽  
Åge Wifstad ◽  
Christopher Dowrick
Keyword(s):  
General Practitioners ◽  
Narrative Analysis ◽  
Mode Competition ◽  
General Applicability ◽  
Naturally Occurring ◽  
Wide Range ◽  
The One ◽  
Narrative Mode ◽  
Modes Of Interaction

In this article, we qualitatively explore the manner and style in which medical encounters between patients and general practitioners (GPs) are mutually conducted, as exhibited in situ in 10 consultations sourced from the One in a Million: Primary Care Consultations Archive in England. Our main objectives are to identify interactional modes, to develop a classification of these modes, and to uncover how modes emerge and shift both within and between consultations. Deploying an interactional perspective and a thematic and narrative analysis of consultation transcripts, we identified five distinctive interactional modes: question and answer (Q&A) mode, lecture mode, probabilistic mode, competition mode, and narrative mode. Most modes are GP-led. Mode shifts within consultations generally map on to the chronology of the medical encounter. Patient-led narrative modes are initiated by patients themselves, which demonstrates agency. Our classification of modes derives from complete naturally occurring consultations, covering a wide range of symptoms, and may have general applicability.

scholarly journals Recent Advancements in Polymer/Liposome Assembly for Drug Delivery: From Surface Modifications to Hybrid Vesicles

Polymers ◽  
2021 ◽  
Vol 13 (7) ◽  
pp. 1027
Author(s):  
Vincenzo De Leo ◽  
Francesco Milano ◽  
Angela Agostiano ◽  
Lucia Catucci
Keyword(s):  
Drug Delivery ◽  
First Generation ◽  
Phospholipid Bilayer ◽  
Bioactive Molecules ◽  
Systemic Delivery ◽  
Molecular Weights ◽  
Liposome Preparation ◽  
Wide Range ◽  
Liposome Surface

Liposomes are consolidated and attractive biomimetic nanocarriers widely used in the field of drug delivery. The structural versatility of liposomes has been exploited for the development of various carriers for the topical or systemic delivery of drugs and bioactive molecules, with the possibility of increasing their bioavailability and stability, and modulating and directing their release, while limiting the side effects at the same time. Nevertheless, first-generation vesicles suffer from some limitations including physical instability, short in vivo circulation lifetime, reduced payload, uncontrolled release properties, and low targeting abilities. Therefore, liposome preparation technology soon took advantage of the possibility of improving vesicle performance using both natural and synthetic polymers. Polymers can easily be synthesized in a controlled manner over a wide range of molecular weights and in a low dispersity range. Their properties are widely tunable and therefore allow the low chemical versatility typical of lipids to be overcome. Moreover, depending on their structure, polymers can be used to create a simple covering on the liposome surface or to intercalate in the phospholipid bilayer to give rise to real hybrid structures. This review illustrates the main strategies implemented in the field of polymer/liposome assembly for drug delivery, with a look at the most recent publications without neglecting basic concepts for a simple and complete understanding by the reader.

scholarly journals Regulation of Cytochrome c Oxidase by Natural Compounds Resveratrol, (–)-Epicatechin, and Betaine

Cells ◽  
2021 ◽  
Vol 10 (6) ◽  
pp. 1346
Author(s):  
Icksoo Lee
Keyword(s):  
Cytochrome C ◽  
Cytochrome C Oxidase ◽  
Model Systems ◽  
Health Improvement ◽  
Published Data ◽  
Mitochondrial Electron Transport Chain ◽  
Naturally Occurring ◽  
Transport Chain ◽  
Wide Range ◽  
Experimental Model Systems

Numerous naturally occurring molecules have been studied for their beneficial health effects. Many compounds have received considerable attention for their potential medical uses. Among them, several substances have been found to improve mitochondrial function. This review focuses on resveratrol, (–)-epicatechin, and betaine and summarizes the published data pertaining to their effects on cytochrome c oxidase (COX) which is the terminal enzyme of the mitochondrial electron transport chain and is considered to play an important role in the regulation of mitochondrial respiration. In a variety of experimental model systems, these compounds have been shown to improve mitochondrial biogenesis in addition to increased COX amount and/or its enzymatic activity. Given that they are inexpensive, safe in a wide range of concentrations, and effectively improve mitochondrial and COX function, these compounds could be attractive enough for possible therapeutic or health improvement strategies.

scholarly journals Sustainable Myrcene-Based Elastomers via a Convenient Anionic Polymerization

Polymers ◽  
2021 ◽  
Vol 13 (5) ◽  
pp. 838
Author(s):  
David Hermann Lamparelli ◽  
Magdalena Maria Kleybolte ◽  
Malte Winnacker ◽  
Carmine Capacchione
Keyword(s):  
Anionic Polymerization ◽  
Sodium Hydride ◽  
Reactivity Ratios ◽  
Molecular Weights ◽  
Styrene Copolymers ◽  
Wide Range ◽  
Elastomeric Materials ◽  
Complete Study ◽  
Anionic Copolymerization ◽  
Trialkylaluminum Derivatives

Soluble heterocomplexes consisting of sodium hydride in combination with trialkylaluminum derivatives have been used as anionic initiating systems at 100 °C in toluene for convenient homo-, co- and ter-polymerization of myrcene with styrene and isoprene. In this way it has been possible to obtain elastomeric materials in a wide range of compositions with interesting thermal profiles and different polymeric architectures by simply modulating the alimentation feed and the (monomers)/(initiator systems) ratio. Especially, a complete study of the myrcene-styrene copolymers (PMS) was carried out, highlighting their tapered microstructures with high molecular weights (up to 159.8 KDa) and a single glass transition temperature. For PMS copolymer reactivity ratios, rmyr = 0.12 ± 0.003 and rsty = 3.18 ± 0.65 and rmyr = 0.10 ± 0.004 and rsty = 3.32 ± 0.68 were determined according to the Kelen–Tudos (KT) and extended Kelen–Tudos (exKT) methods, respectively. Finally, this study showed an easy accessible approach for the production of various elastomers by anionic copolymerization of renewable terpenes, such as myrcene, with commodities.

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