The Refractometry of Rubber and Gutta-Percha Hydrocarbons. I. The Influence of Depolymerization and Oxidation on the Refractive Exponents of These Hydrocarbons

1933 ◽  
Vol 6 (1) ◽  
pp. 92-100 ◽  
Author(s):  
F. Kirchhof
Keyword(s):  
Laboratory Testing ◽  
Degree Of Polymerization ◽  
Index Of Refraction ◽  
Natural Substances ◽  
Gutta Percha ◽  
Initial Stage ◽  
Points Of View ◽  
Insight Into ◽  
Osmotic Behavior

Abstract 1. The acetone-extractable substances from different natural rubbers have an appreciable influence on the index of refraction of their hydrocarbons. This influence is different in the case of Hevea rubbers from that in the case of African rubbers, for example. 2. The indices of refraction of different kinds of raw rubber after extraction likewise differ appreciably. These differences may be attributed in part to the different quantities of benzene-insoluble non-rubber substances, in part to differences in the degree of polymerization of the different hydrocarbons. 3. A study of the influence of mastication, depolymerization by heat and oxidation on the magnitude of the light refractive exponents of rubber and gutta-percha shows that there are characteristic differences between the two kinds of hydrocarbons, at least as far as the initial stage of oxidation is concerned. 4. From the purely practical and laboratory-testing points of view, it is possible to detect quickly and easily differences in the same kinds of raw rubber which are originally present or result from mastication, and to follow the course of mastication. 5. Furthermore it appears possible to draw conclusions regarding the constitution of rubber and gutta-percha hydrocarbons from differences in their viscosimetric and osmotic behavior. Accordingly the refractometry of rubber and gutta-percha hydrocarbons may furnish a new way of gaining a deeper insight into the structure of these natural substances.

scholarly journals “Nothing is ever easy”: Parent Perceptions of Intensity in Their Gifted Adolescent Children

2019 ◽  
Author(s):  
Kate Guthrie
Keyword(s):  
Thematic Analysis ◽  
Challenging Behaviors ◽  
Parent Perceptions ◽  
Interview Study ◽  
Gifted Children ◽  
Asynchronous Development ◽  
Depth Interview ◽  
The World ◽  
Points Of View ◽  
Insight Into

Due to asynchronous development, gifted children often experience the world differently than their same-aged peers. Some experience unique intensities, or overexcitabilities, that render modifications in teaching and parenting. These intensities typically take on characteristics of emotional, intellectual, imagination, psychomotor, or sensual overexcitability. In this in-depth interview study, I explored parent perceptions of intensity in their gifted adolescent children. Three mothers participated and completed the Overexcitability Inventory for Parents-Two (OIP-II) prior to each interview. The parent responses to the OIP-II served as an elicitation device to begin our conversations. Thematic analysis revealed three main themes among the participants’ perceptions: (1) challenging behaviors of intense gifted children, (2) consequences of intensity, and (3) a parent’s search for understanding. These findings inform the understanding of intensity and overexcitability from parents’ points of view and provide insight into how intense gifted children behave outside of the classroom. I conclude the article with questions to consider regarding how to better support parents of young gifted children.

A Single Xyloglucan Xylosyltransferase is Sufficient for Generation of the XXXG Xylosylation Pattern of Xyloglucan

2021 ◽  
Author(s):  
Ruiqin Zhong ◽  
Dennis R Phillips ◽  
Zheng-Hua Ye
Keyword(s):  
Recombinant Proteins ◽  
Cell Walls ◽  
Degree Of Polymerization ◽  
Primary Cell ◽  
Hek293 Cells ◽  
Biochemical Mechanism ◽  
The Third ◽  
Insight Into

Abstarct Xyloglucan is the most abundant hemicellulose in the primary cell walls of dicots. Dicot xyloglucan is the XXXG-type consisting of repeating units of three consecutive xylosylated Glc residues followed by one unsubstituted Glc. Its xylosylation is catalyzed by xyloglucan 6-xylosyltransferases (XXTs) and there exist five XXTs (AtXXT1-5) in Arabidopsis. While AtXXT1and AtXXT2 have been shown to add the first two Xyl residues in the XXXG repeat, which XXTs are responsible for the addition of the third Xyl residue remains elusive although AtXXT5 was a proposed candidate. In this report, we generated recombinant proteins of all five Arabidopsis XXTs and one rice XXT (OsXXT1) in the mammalian HEK293 cells and investigated their ability to sequentially xylosylate Glc residues to generate the XXXG xylosylation pattern. We found that like AtXXT1/2, AtXXT4 and OsXXT1 could efficiently xylosylate the cellohexaose (G6) acceptor to produce mono- and di-xylosylated G6, whereas AtXXT5 was only barely capable of adding one Xyl onto G6. When AtXXT1-catalyzed products were used as acceptors, AtXXT1/2/4 and OsXXT1 but not AtXXT5 were able to xylosylate additional Glc residues to generate tri- and tetra-xylosylated G6. Further characterization of the tri- and tetra-xylosylated G6 revealed that they had the sequence of GXXXGG and GXXXXG with three and four consecutive xylosylated Glc residues, respectively. In addition, we have found that although tri-xylosylation occurred on G6, cello-oligomers with a degree of polymerization of 3 to 5 could only be mono- and di-xylosylated. Together, these results indicate that each of AtXXT1/2/4 and OsXXT1 is capable of sequentially adding Xyl onto three contiguous Glc residues to generate the XXXG xylosylation pattern and these findings provide new insight into the biochemical mechanism underlying xyloglucan biosynthesis.

GENERALIZATION OF OLYMPIAD PROBLEMS WITH DYNAMIC SOFTWARE

2021 ◽  
Vol 12 (1) ◽  
pp. 249-255
Author(s):  
Sava Grozdev ◽  
◽  
Veselin Nenkov ◽  
Keyword(s):  
Geometer's Sketchpad ◽  
International Mathematical ◽  
Points Of View ◽  
Dynamic Software ◽  
Program Software ◽  
Insight Into ◽  
Gaining Insight

Various meaningful generalizations could be obtained after gaining insight into some mathematical assertions from different points of view. Generalizations of two problems from International Mathematical Olympiad papers are shown when the details are combined with the opportunities of the program software „The Geometer’s Sketchpad “ (GSP).

scholarly journals Pulse Duration and Wavelength Effects of Laser Ablation on the Oxidation, Hydrolysis, and Aging of Aluminum Nanoparticles in Water

Nanomaterials ◽  
2019 ◽  
Vol 9 (5) ◽  
pp. 767 ◽  
Author(s):  
Ke Zhang ◽  
Dmitry S. Ivanov ◽  
Rashid A. Ganeev ◽  
Ganjaboy S. Boltaev ◽  
Pandiyalackal S. Krishnendu ◽  
...  
Keyword(s):  
Pulse Duration ◽  
Morphological Transformation ◽  
Short Pulses ◽  
Al Nanoparticles ◽  
Initial Stage ◽  
Three Stages ◽  
Points Of View ◽  
Hydrolysis Of ◽  
Stable Stage

We analyzed the formation of the aluminum (Al) nanoparticles (NPs) with triangular shape obtained by ablating Al bulk in liquid using pulses with different durations (5 ns, 200 ps, and 30 fs) and wavelengths (355 nm, 800 nm, and 1064 nm). We report three stages of synthesis and aging of Al NPs: Formation, transformation, and stable stage. The NPs prepared by different pulses are almost identical at the initial stage. The effects of duration and wavelength of the ablation pulses on the aging of NPs are revealed. Pulse duration is determined to be essential for morphological transformation of NPs, while pulse wavelength strongly influences particle sizes. NPs produced by ultra-short pulses have smaller sizes and narrow size distribution. We demonstrate that oxidation and hydrolysis of Al in water are the results of ablation for all pulse durations and wavelengths, which also strongly modify the preferable reaction path of NPs in water, thus affecting the composition and morphology of triangle NPs. The results of modeling of the NPs generation in water due to a 50 ps laser pulse interacting with a thick Al target are presented. Water-based effects in the formation of NPs, their evolution, and solidification are considered from the mechanical and thermophysical points of view. The detailed analysis of the modeling results allowed for determination of the main mechanism responsible for the ablation process followed by the NPs formation.

Distribution of the Molecule Weight and Grain Size of Medium Temperature Phenol Formaldehyde Resin

2011 ◽  
Vol 217-218 ◽  
pp. 359-362
Author(s):  
Han Jian ◽  
Yie Guo
Keyword(s):  
Grain Size ◽  
Mass Spectrum ◽  
Addition Reaction ◽  
Phenol Formaldehyde ◽  
Phenol Formaldehyde Resin ◽  
Degree Of Polymerization ◽  
Formaldehyde Resin ◽  
Medium Temperature ◽  
Initial Stage ◽  
Analysis Instrument

The molecule weight and distribution of molecule weight of a kind of medium temperature phenol formaldehyde resin（MTPF）was detected through Liquid Chromatogram-mass spectrum instrument（LC-MS）．The result showed that the distribution scope of molecule weight of the MTPF during the initial stage was approximately 200-400，and the degree of polymerization of the MTPF molecule was 2-4，At the same time，the MTPF during initial stage still has a certain amount of medium outcome hydroxymethyl phenol which was formed through the addition reaction between phenol and formaldehyde．The detection result，from the MTPF during initial stage through ZEN3600 nanometer grain analysis instrument， proved that the grain size of the MTPF during initial stage was about 80-180nm，and the distribution of the grain size presented a normal one that the grain size 96-130nm was about 67%．

Recalibrating Reform

2018 ◽  
Vol 35 (2) ◽  
pp. 183-222
Author(s):  
Michele Cabrini
Keyword(s):  
Eighteenth Century ◽  
Creative Process ◽  
Ongoing Debate ◽  
Unique Position ◽  
Literary Sources ◽  
Opera Seria ◽  
Return Home ◽  
Points Of View ◽  
Insight Into ◽  
Captive Condition

The opera Telemaco, with a libretto by Marco Coltellini and music by Christoph Gluck, occupies a unique position as an opera seria that negotiates both tradition and reform. Scholars have long criticized the opera because of its ill-shaped libretto and uneven musical setting. This article contributes to the ongoing debate about operatic reform by reevaluating Telemaco based on its literary sources—Homer’s Odyssey and Fénelon’s novel Télémaque (1699). The absorption of Homer and Fénelon into the fabric of Telemaco goes well beyond adaptation, touching both its general dramaturgy and the specific creation of its characters. Set on the island of Circe, Coltellini's libretto echoes the timeless, liminal status of the corresponding islands (Circe’s and Calypso’s) found in Homer and Fénelon. The characters reflect and blend features of their literary counterparts. They fall into two groups: those who fight their captive condition through impetuous behavior (Circe and Telemachus) and those who attempt to circumvent their predicament by clinging to a golden past (Asteria) or yearning for a hopeful future (Ulysses’s desire to return home). Gluck’s expression of the characters’ longing and identity, achieved through a manipulation of form and textual re-composition, thus implies multiple temporal directions, suggesting a series of synchronic, revolving points of view that challenge the diachronic unfolding of events typically associated with opera reform in the eighteenth century. This method of analysis therefore offers insight into the creative process and helps refine our understanding of reformist opera, both in Gluck’s output and broader eighteenth-century operatic practice.

Isoprene and Rubber. Part 44. Viscosity Measurements of Squalene and Hydrosqualene Solutions

1936 ◽  
Vol 9 (4) ◽  
pp. 573-578
Author(s):  
H. Staudinger ◽  
H. P. Mojen
Keyword(s):  
Physical Properties ◽  
General Relation ◽  
Basic Structure ◽  
Degree Of Polymerization ◽  
Specific Viscosity ◽  
Viscosity Measurements ◽  
Molecular Weights ◽  
Gutta Percha ◽  
Rubber Part

Abstract The physical properties of highly polymerized substances, which are composed of fiber molecules, depend on the lengths of the chains of these fiber molecules. Thus tensile strength, elasticity, tendency to swell in solvents, and above all viscosity, are dependent on the length of chain of the particular substance. Among the substances, the properties of which vary thus, are rubber, gutta-percha, and balata. Since the length of fiber molecules can vary within wide limits, such physical properties as those mentioned above show wide variations in the case of rubber, gutta-percha, and balata. This is evident for example by a comparison of the properties of unmasticated rubber, which consists of long fiber molecules of a degree of polymerization of 2000, with the properties of masticated rubber, the greatly dissociated molecules of which have a degree of polymerization of only 500. The determination of the length of the fiber molecules is therefore of great importance in the case of highly polymerized substances. It has already been proved in past experiments with members of a series of homologous polymers, i. e., of substances the macromolecules of which have the same basic structure and differ only in length, that the molecular weights can be determined from viscosity measurements. This determination is based on the fact that there is a general relation between the specific viscosity and the length of the dissolved molecules, which can be expressed by the formula:

scholarly journals Insight into the Evolution of the Cellulose Microstructure Through the Enzyme Pretreatment Method

2021 ◽  
Author(s):  
Qijun Ding ◽  
Limin Jing ◽  
Wenjia Han ◽  
Yanpeng Guan ◽  
Yifei Jiang ◽  
...  
Keyword(s):  
Degree Of Polymerization ◽  
Correlation Spectroscopy ◽  
X Ray Diffraction ◽  
Pretreatment Method ◽  
X Ray ◽  
Cellulosic Fibers ◽  
Enzyme Pretreatment ◽  
Theoretical Support ◽  
Derivative Analysis ◽  
Insight Into

Abstract In this work, the changes of properties and microstructure of cellulose (bleached hardwood kraft pulp (BHKP)) subjected to different enzyme pretreatment times (0–10 h) were explored for further fibrillation. The various properties of the pretreated cellulose gradually decrease with the elapse of time relative to the pristine material, such as yield, water retention value, aspect ratio and degree of polymerization, etc. Enzyme pretreatment can promote the peeling of fibrils and loosen the amorphous areas of cellulose identified by Scanning Electron Microscope (SEM) and X-ray diffraction (XRD). A thorough investigation of the relation between pretreatment and evolution of inter-/intra-molecular H-bonds in cellulose was conducted including content and cleave sequence of H-bonds by Fourier transform infrared spectroscopy (FTIR), second derivative analysis and generalized two-dimensional correlation spectroscopy (2DCOS). The intermolecular H-bonds with the most significant decrease in content was cleaved first relative to the intramolecular H-bonds. These discoveries provide theoretical support to more effective pretreatment method for commercial production of fibrils from cellulosic fibers.

scholarly journals Role of Foreseeability in Imposition of Civil Liability

2021 ◽  
Vol 2 (20) ◽  
pp. 268-286
Author(s):  
Edijs Brants
Keyword(s):  
Strict Liability ◽  
Theoretical Perspective ◽  
Civil Liability ◽  
Article Analysis ◽  
Points Of View ◽  
Insight Into

The purpose of this article is to offer an insight into the role of foreseeability in imposition of civil liability. The article contains analysis of the principle of foresee­ability from various points of view, for example, by analysing it from the perspective of the general (fault-based) model of liability as well of the strict liability. Likewise, the article analysis the role of foreseeability during determination of preconditions to civil liability, for example, by introducing it into the concepts of “fault” and “causation”. The aspects referred to in this article are predominantly analysed from the theoretical perspective. The article references various legal sources from different countries, which allows other legal scholars to use the conclusions offered herein.

scholarly journals Imputation of Missing Gas Permeability Data for Polymer Membranes using Machine Learning

2020 ◽  
Author(s):  
Qi Yuan ◽  
Mariagiulia Longo ◽  
Aaron Thornton ◽  
Neil B. McKeown ◽  
Bibiana Comesana-Gandara ◽  
...  
Keyword(s):  
Machine Learning ◽  
Energy Efficient ◽  
Missing Values ◽  
Gas Permeability ◽  
Polymer Membranes ◽  
Gas Separations ◽  
Initial Stage ◽  
Sparse Features ◽  
Potential Use ◽  
Insight Into

<p><a>Polymer-based membranes can be used for energy efficient gas separations. Successful exploitation of new materials requires accurate knowledge of the transport properties of all gases of interest. An open source database of such data is of significant benefit to the research community. The Membrane Society of Australasia (https://membrane-australasia.org/) hosts a database for experimentally measured and reported polymer gas permeabilities. However, the database is incomplete, limiting its potential use as a research tool. Here, missing values in the database were filled using machine learning (ML). The ML model was validated against gas permeability measurements that were not recorded in the database. Through imputing the missing data, it is possible to re-analyse historical polymers and look for potential “missed” candidates with promising gas selectivity. In addition, for systems with limited experimental data, ML using sparse features was performed, and we suggest that once the permeability of CO<sub>2</sub> and/or O<sub>2</sub> for a polymer has been measured, most other gas permeabilities and selectivities, including those for CO<sub>2</sub>/CH<sub>4</sub> and CO<sub>2</sub>/N<sub>2</sub>, can be quantitatively estimated. This early insight into the gas permeability of a new system can be used at an initial stage of experimental measurements to rapidly identify polymer membranes worth further investigation.</a></p>

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