bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of Pruning on Economics of Production of Indeterminate Variety of Tomato (Lycopersicon esculentum Mill.) in Polyhouse
Authors: Yadav Anurag , Singh D.P. , Singh R.B. , Rajeev . , Diwakar Mandeep Kumar , Maurya Shashikant , Singh Utkarsh Pratap , Maurya Anil Kumar , Rathore Ayush , Singh Vikash Pratap
Published: May 2024

An experiment was conducted at the Department of Vegetable Science, CSAUAT- Kanpur to investigate the role of plant spacing and pruning in economics of production of indeterminate variety of tomato in polyhouse rabi season 2023-2024.The variety under observation is NS4266 .Although cultivation under polyhouse condition is capital intensive process but it is also highly remunerative. The experiment is conducted in randomized block design with four treatment and four replication. Pruning under single stem is best over all the other treatments and is comparative to double stem and triple stem in some cases. Single stem has prolonged market period and highly sustainable in nature.
Correlation between Rice Weevil Infestation Sitophilus oryzae (Linnaeus) and Seed Quality Parameters of Maize (Zea mays. L) Seed
Authors: M Pramod Kumar , Padmasri A. , Sridevi G. , Azam M. Mohibbe
Published: May 2024

The experiment was conducted at the Seed Research and Technology Centre, PJTSAU, Rajendranagar, Hyderabad, to investigate the impact of Sitophilus oryzae on the seed quality parameters of maize. Samples weighing 500g of maize variety DHM-117 were placed in plastic jars in three replications S. oryzae adults of 0, 5, 10, 15, and 20 pairs were separately released into each replicate of the maize seeds then these jars were placed in an incubator set at 25°C and 75% humidity. These jars were covered with lids equipped with aeration facilities. The adult emergence, germination percentage and moisture content were evaluated every two months six months. An inverse correlation was observed between adult emergence with germination percentage and seedling vigour index while, adult emergence showed a positive correlation with moisture content.
Monetary Policy, Digitalisation and Banking Industry Performance in Nigeria
Authors: Enebeli-Uzor Sunday , Mukhtar Adam
Published: May 2024

In the evolving financial landscape of Nigeria, the interplay between monetary policy and digitalization significantly influences the performance metrics of banks. This study explores the multifaceted impact of these two critical factors on the Nigerian banking sector. Monetary policy, orchestrated by the Central Bank of Nigeria, regulates the economy's money supply, affecting banks' lending behaviors and liquidity. Digitalization, on the other hand, offers a transformative potential for banks to enhance operational efficiency, customer experience, and service delivery through technological advancements. The study examines how money supply, lending rate and digitalization (proxied by mobile cell subscription) affect banks’ financial performance, focusing on bank credit and liquid assets, while controlling for inflation and exchange rate variables. It also examines the interaction between digitalization and monetary policy variables on bank performance. Employing an interactive multiple regression model, the study analyzes time series data from 1996 to 2022 sourced from the World Bank. Findings indicate that while stringent monetary policies can constrain bank performance by tightening credit and reducing liquidity, digitalization provides an opportunity for banks to counteract these effects through enhanced efficiency. However, the successful integration of digital technologies is contingent upon adequate investment, regulatory support, and strategic alignment with the banks’ core objectives. The study concludes that Nigerian banks must adeptly manage monetary policy fluctuations and leverage digitalization to sustain and enhance performance. These insights could guide policy formulation and strategic decision-making within the banking industry.
Simvastatin treatment prevents oxidative damage to DNA in whole blood leukocytes of dyslipidemic type 2 diabetic patients
Authors: Manfredini Vanusa , Biancini Giovana Brondani , Vanzin Camila Simioni , Dal Vesco Anna Maria Ribeiro , Cipriani Franciele , Biasi Lidiana , Treméa Roberta , Deon Marion , Peralba Maria do Carmo Ruaro , Wajner Moacir , Vargas Carmen Regla
Published: June 2010

Type 2 diabetes (T2D) is associated with increased oxidative stress as indicated by elevated levels of lipid peroxidation and protein oxidation products. Since reactive oxygen species (ROS) can cause damage to biological macromolecules including DNA, this study investigated oxidative damage to DNA using the alkaline (pH > 13) comet assay in peripheral whole blood leukocytes sampled from 15 dyslipidemic T2D patients treated with simvastatin (20 mg/day), 15 dyslipidemic T2D patients not treated with simvastatin, 20 non‐dyslipidemic T2D patients, and 20 healthy individuals (controls). Our results showed a greater DNA migration in terms of damage index (DI) (p < 0.01) in the dyslipidemic T2D patients not treated with statin (DI = 67.70 ± 10.89) when compared to the dyslipidemic T2D patients under statin treatment (DI = 47.56 ± 7.02), non‐dyslipidemic T2D patients (DI = 52.25 ± 9.14), and controls (DI = 13.20 ± 6.40). Plasma malondialdehyde (MDA) and C‐reactive protein (CRP) levels were also increased and total antioxidant reactivity (TAR) and paraoxonase activity (PON1) decreased in non‐dyslipidemic T2D patients and dyslipidemic T2D non‐treated with simvastatin. We also found that DI was inversely correlated with TAR (r = −0.61, p < 0.05) and PON1 (r = −0.67, p < 0.01). In addition, there was a significant positive correlation between DI and CRP (r = 0.80, p < 0.01). Our results therefore indicate that simvastatin treatment plays a protective role on oxidative damage to DNA in dyslipidemic T2D patients probably reflecting a general decrease in oxidative stress in these patients. Copyright © 2010 John Wiley & Sons, Ltd.
In vitro effects of 2‐methoxyestradiol‐bis‐sulphamate on the non‐tumorigenic MCF‐12A cell line
Authors: Vorster Christiaan Jacob Johan , Joubert Anna Margaretha
Published: June 2010

A priority in recent anti‐cancer drug development has been attaining better side‐effect profiles for potential compounds. To produce highly specific cancer therapies it is necessary to understand both the effects of the proposed compound on cancer and on normal cells comprising the rest of the human body. Thus in vitro evaluation of these compounds against non‐carcinogenic cell lines is of critical importance. One of the most recent developments in experimental anti‐cancer agents is 2‐methoxyestradiol‐bis‐sulphamate (2ME‐BM), a sulphamoylated derivative of 2‐methoxyestradiol. The aim of this study was to evaluate the in vitro effects of 2ME‐BM on cell proliferation, morphology and mechanisms of cell death in the non‐carcinogenic MCF‐12A breast epithelial cell line. The study revealed changes in proliferative capacity, morphology and cell death induction in response to 2ME‐BM exposure (24 h at 0.4 µM). Microscopy showed decreased cell density and cell death‐associated morphology (increased apoptotic characteristics), a slight increase in acidic intracellular vesicles and insignificant ultra‐structural aberrations. Mitotic indices revealed a G2M‐phase cell cycle block. This was confirmed by flow cytometry, where an increased fraction of abnormal cells and a decrease in cyclin B1 levels were observed. These results evidently demonstrate that the non‐carcinogenic MCF‐12A cell line is less susceptible when compared to 2ME‐BM‐exposed cancer cell lines previously tested. Further in vitro research into the mechanism of this potentially useful compound is warranted. Copyright © 2010 John Wiley & Sons, Ltd.
ChemInform Abstract: Present State of the Art and Future Challenges in the Hydrodesulfurization of Polyaromatic Sulfur Compounds.
Authors: WHITEHURST D. D. , ISODA T. , MOCHIDA I.
Published: June 2010

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
ChemInform Abstract: RECAP — Retrosynthetic Combinatorial Analysis Procedure: A Powerful New Technique for Identifying Privileged Molecular Fragments with Useful Applications in Combinatorial Chemistry.
Authors: LEWELL X. Q. , JUDD D. B. , WATSON S. P. , HANN M. M.
Published: June 2010

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
Simultaneous detection of genetically modified organisms by multiplex ligation‐dependent genome amplification and capillary gel electrophoresis with laser‐induced fluorescence
Authors: García‐Cañas Virginia , Mondello Monica , Cifuentes Alejandro
Published: June 2010

In this work, an innovative method useful to simultaneously analyze multiple genetically modified organisms is described. The developed method consists in the combination of multiplex ligation‐dependent genome dependent amplification (MLGA) with CGE and LIF detection using bare‐fused silica capillaries. The MLGA process is based on oligonucleotide constructs, formed by a universal sequence (vector) and long specific oligonucleotides (selectors) that facilitate the circularization of specific DNA target regions. Subsequently, the circularized target sequences are simultaneously amplified with the same couple of primers and analyzed by CGE‐LIF using a bare‐fused silica capillary and a run electrolyte containing 2‐hydroxyethyl cellulose acting as both sieving matrix and dynamic capillary coating. CGE‐LIF is shown to be very useful and informative for optimizing MLGA parameters such as annealing temperature, number of ligation cycles, and selector probes concentration. We demonstrate the specificity of the method in detecting the presence of transgenic DNA in certified reference and raw commercial samples. The method developed is sensitive and allows the simultaneous detection in a single run of percentages of transgenic maize as low as 1% of GA21, 1% of MON863, and 1% of MON810 in maize samples with signal‐to‐noise ratios for the corresponding DNA peaks of 15, 12, and 26, respectively. These results demonstrate, to our knowledge for the first time, the great possibilities of MLGA techniques for genetically modified organisms analysis.
The loudness dependence auditory evoked potential is insensitive to acute changes in serotonergic and noradrenergic neurotransmission
Authors: Oliva Jessica , Leung Sumie , Croft Rodney J. , O'Neill Barry V. , O'Kane Joanne , Stout Julie , Phan K. Luan , Nathan Pradeep J.
Published: June 2010

Background

The loudness dependence of the auditory evoked potential (LDAEP) has been proposed as an electrophysiological marker for assessing serotonergic function in vivo in humans, although accumulating evidence suggests that it is insensitive to acute changes in serotonergic neurotransmission. Very little is known about the sensitivity of the LDAEP to other neurotransmitter systems including the noradrenergic system. The current study examined the effects of noradrenergic modulation as well as serotonergic modulation on the LDAEP.

Methods

The study utilised a double‐blind placebo‐controlled design in which the LDAEP in 17 healthy males and females was tested following acute administration of each of citalopram (20 mg), reboxetine (4 mg) and placebo.

Results

Neither citalopram nor reboxetine modulated the LDAEP relative to placebo treatment (p > 0.05).

Conclusion

These findings suggest that the LDAEP is insensitive to acute changes in serotonergic or noradrenergic neurotransmission and thus is a poor pharmacodynamic marker of these systems. Copyright © 2010 John Wiley & Sons, Ltd.
Effect of nicotine on saccadic eye movement latencies in non‐smokers
Authors: Bowling Alison C. , Donnelly James F.
Published: June 2010

Objective

Recently, saccadic eye movement tasks have been used to assess the effects of nicotine on higher cognitive processes, including inhibitory control. Saccadic task switching methods suggest that there is prolonged inhibition of the saccadic eye movement system following antisaccade trials. The objective of this research was to examine effects of nicotine on inhibition using saccadic task switching paradigms.

Methods

Nicotine and placebo lozenges were administered on separate days to 40 non‐smokers who performed prosaccade and antisaccade tasks. In addition, participants performed a series of trials in which prosaccade and antisaccade tasks were switched. Eye movement latencies were recorded.

Results

Participants responded significantly faster for the nicotine condition than for the placebo condition. A switch benefit was observed for only placebo antisaccade trials, in that latencies of repetition trials were significantly longer than those of switch trials. In addition, an analysis of the repetition trials showed an interaction between saccade type and sequence position for the placebo condition, but not the nicotine condition.

Conclusion

Inhibition persists after antisaccade trials in a switching paradigm, but that the duration of this inhibition is reduced by nicotine. Copyright © 2010 John Wiley & Sons, Ltd.
N‐Boc‐Histidine‐Capped PLGA‐PEG‐PLGA as a Smart Polymer for Drug Delivery Sensitive to Tumor Extracellular pH
Authors: Chang Guangtao , Li Chong , Lu Weiyue , Ding Jiandong
Published: June 2010

A pH‐sensitive polymer was synthesized by introducing the N‐Boc‐histidine to the ends of a PLGA‐PEG‐PLGA block copolymer. The synthesized polymer was confirmed to be biodegradable and biocompatible, well dissolved in water and forming micelles above the CMC. DOX was employed as a model anticancer drug. In vitro drug release from micelles of N‐Boc‐histidine‐capped PLGA‐PEG‐PLGA exhibited significant difference between pH = 6.2 and pH = 7.4, whereas DOX release from micelles composed of un‐capped virgin polymers was not significantly sensitive to medium pH. Uptake of DOX from micelles of the new polymer into MDA‐MB‐435 solid tumor cells was also observed, and pH sensitivity was confirmed. Hence, the N‐Boc‐histidine capped PLGA‐PEG‐PLGA might be a promising material for tumor targeting.

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Synthesis and Characterization of New Polyurea Elastomers by Sol/Gel Chemistry
Authors: Sánchez‐Ferrer Antoni , Rogez Daniel , Martinoty Philippe
Published: June 2010

A series of elastomers based on polyurea chemistry is synthesized by crosslinking amino‐terminated polyethers with a triisocyanate using an appropriate solvent, which slowed down the reactivity of the amino groups. Control of the reactivity allows the shaping of the material, and films of defined thickness can be achieved for mechanical testing. The strength of the final network can be tuned by the crosslinking density of the network chemical constitution. The resulting materials show a good thermal stability and promising mechanical enhancement.

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Patterning of Tailored Polycarbonate Based Non‐Chemically Amplified Resists Using Extreme Ultraviolet Lithography
Authors: Yu Anguang , Liu Heping , Blinco James P. , Jack Kevin S. , Leeson Michael , Younkin Todd R. , Whittaker Andrew K. , Blakey Idriss
Published: June 2010

A series of high‐performance polycarbonates have been prepared with glass‐transition temperatures and decomposition temperatures that are tunable by varying the repeat‐unit chemical structure. Patterning of the polymers with extreme UV lithography has been achieved by taking advantage of direct photoinduced chain scission of the polymer chains, which results in a molecular‐weight based solubility switch. After selective development of the irradiated regions of the polymers, feature sizes as small as 28.6 nm have been printed and the importance of resist‐developer interactions for maximizing image quality has been demonstrated.

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Kalorimetrische Messungen der Kristallisations‐und Schmelzvorgänge an Polymeren
Authors: Müller F. H. , Martin H.
Published: June 2010

Crystallizing and melting of polymers as a function of sample history is investigated by means of a differential thermal analytic method developed for quantitative evaluation. Crystallization and the subsequent melting of the same polymer occur at temperatures differing by 12 to 18°C. The melt temperature and the time of keeping the sample in the molten state, the cooling rate and the course of cooling have a reproducible effect on the subsequent melting. The crystallization is followed at constant temperature, and the crystallization rate is evaluated. Application of the Avrami method gives agreement with similar density and refractive index measurements.
Differentialkalorimetrische Messungen an verschieden verzweigten und verschieden chlorierten polyäthylenen in Verbindung mit Röntgenmessungen
Authors: Hellmuth E. , Kilian H. G. , Müller F. H.
Published: June 2010

Branched or partially chlorinated polyethylenes may be considered as copolymers, the branching or chlorinated sites forming the noncryatallizing components. Melting curves are calculated according to Flory and compared to experimental curves on well annealed samples. A normalized conversion (fitting) function is obtained which is largely independent of the nature and concentration of the noncrystallizing component. By means of the fitting function conclusions are possible on the deviation from tlier mo dynamic equilibrium, on the crystallite size distribution and on the heterogeneous small angle scattering behavior.
Characterization of molecular weight distributions in high polymers
Authors: Billmeyer Fred W.
Published: June 2010

In this review paper, these types of molecular weight distribution found in typical polymers are described. It is pointed out that procedures for fractionating polymers usually yield incomplete information on molecular weight distribution unless the fractions are characterized for molecular weight. In addition, measurement of different average molecular weights can itself give limited information on molecular weight distribution breadth. Experimental methods for molecular weight determination are described with emphasis on range of applicability, precision, accuracy, convenience, and cost. For measuring number‐average molecular weight, the thermodynamic methods of cryoscopy, ebulliometry, and osmometry have proven absolute accuracy. The thermoelectric differential vapor pressure technique, while a transport rather than a thermodynamio method, is simple and, in most cases, accurate. Weigh average molecular weight can be measured by light scattering, equilibrium ultracentrifugation, and approach‐to‐equilibrium ultracentrifugation, all thermodynamic methods. Transport properties such as the sedimentation constant, the diffusion constant, the intrinsic viscosity, or the Newtonian melt viscosity, can be empirically correlated with molecular weight. Although in principle these properties can be combined in pairs to yield molecular weights without resort to outside calibration, as in the sedimentation transport method, the results of such treatments must be applied with considerable caution to random coil polymers.
The temperature dependence of the specific refractive index increment of polyethylene in various solvents
Authors: Chiang R.
Published: June 2010

The specific refractive index increment, dn/dc, of polyethylene in α‐chloronaphthalene, tetralin, and n‐decane bas been determined as a function of temperature in the range of 50–80°C. The value of dn/dc was found to be a linear function of the refractive index of the solvent. The temperature coefficient of dn/dc of polyethylene in α‐chloronaphthalene, tetralin, and n‐decane was found to be approximately 0.1 × 10−4, 0.96 × 10−4, and 2.43 × 10−4 cc./g. °C, respectively. There results are interpreted on the basis of the Gladstone‐Dale equation. A simple modification of the Brice‐Phoenix differential refractometer for use at moderately high temperatures is described.
Morphological foundations of fiber properties
Authors: Rebenfeld Ludwig
Published: June 2010

Structural theories which have been developed to interpret the chemical, physical, and mechanical properties of fibers are reviewed, with particular emphasis on the natural fibers. It is pointed out that many of the current theories of fiber structure derive from early concepts of the natural cellulosic or vegetable fibers. The micellar, the fringed micellar, and the fringed fibrillar theories, as well ay the concept of lateral order distribution are presented. The growth and development of cotton fibers are discussed and variations in structure are shown to be reflected in their properties. In this connection fibrillar orientation and helical reversals in cotton fibers are particularly important. The complex organochemical and supermolecular structure of keratin fibers is presented and is shown to be related to the chemical and mechanical properties of these fibers. Cortical asymmetry is a unique structural feature of keratin fibers which is responsible for the characteristic three‐dimensional crimp of wool fibers. The well‐known supercontraction of keratin fibers in a variety of chemical systems is discussed in terms of a chemical mechanism involving sulfhydryl‐disulfide interchange.
The permeability of poly(ethyl methacrylate) to gases and water vapor
Authors: Stannett V. , Williams J. L.
Published: June 2010

The permeabilities, diffusivities and solubilities of He, Ne, A, O2, N2, Kr, CO2, H2S, and H2O in poly(ethyl methacrylate) have been measured above and below the glass temperature. Water showed a small increase in solubility when the polymer was heated above the glass temperature. Water also showed anomalous behavior in that the solubilities calculated from the permeability constants and the time‐lag diffusion constants are much less than those measured by direct weighing. The behavior had been found previously with other polymers and has been interpreted in terms of the clustering of water molecules in the polymer. The Arrhenius plots of the permeability and diffusion constants for water showed the change in slope at the glass temperature reported to occur with many gases and vapors through other polymers. The gases, however, showed no change in slope even with large molecular size gases such as silicon tetrafluoride and sulfur hexafluoride. The results found with water are interpreted as due to the plasticizing effect of the penetrant when the polymer is above the glass temperature. In the case of the gases, the lack of a transition effect is interpreted in terms of the relative sizes of the gas molecule and the average hole she of the polymer. The energies of activation for diffusion were found to be proportional to the 1.6 power of the molecular diameter of the; penetrants, i.e., intermediate between that found for rubber and for both poly(vinyl acetate) and poly(ethylene terephthalate).
Polyethylene‐encapsulated cellulose
Authors: Herman D. F. , Kruse U. , Brancato J. J.
Published: June 2010

An encapsulation process is described in which cellulose fibers were enveloped with sheaths of polyethylene by the use of transition‐metal catalysts. Cellulose‐catalyst interactions resulted in a fiber surface completely covered with initiating sites, and growth of polymer occurred from the fiber surface outward to form a shell around each individual fiber. Removal of moisture and in situ catalyst formation were found to be essential for successful encapsulation. Catalyst interactions during different stages of formation were studied by following the absorption of the various catalyst components on cellulose. Active sites on fiber surfaces were postulated to have been formed by interaction with TiCl4 and by reaction of reduced transition metal compounds with electron donor groups in the cellulose. Polymer growth was followed in a series of electron microphotographs and polyp‐like spherical polyethylene particles were observed at an early stage in the polymerization. It was concluded that encapsulation was a chemical means of placing polymer around a fiber core and not a grafting reaction. Fiber properties, uses of encapsulated cellulose, and conversion into web structures by use of paper making techniques were also discussed.
Brightness reversion of birch sulfate pulp
Authors: Croon Ingemar , Dillén Sten , Olsson Jan‐Erik
Published: June 2010

Three methods of improving brightness stability have been examined: (1) Avoidance of chlorination of extractive components and the residual resin. (2) Modification of the hemicellulose by high‐temperature treatment of the pulp to remove xylan components of poor brightness stability. (3) Maximum reduction of the residual lignin in the pulp. The results of the three methods have been compared and an examination of their combined effect has thrown light on the main cause of brightness reversion in each case. The chlorinated extractives adversely affect the brightness stability during aging in a dry atmosphere, and the reversion in this case is due to degradation mainly of carbohydrates by the hydrogen chloride liberated from the chlorinated extractives. Different fractions of the extractives have been tested with respect to their ability to promote this effect. It would seem that the brightness stability of the pulp is dependent on its carbohydrate composition. An aqueous treatment of the pulp at a high temperature removes some hemicellulose components sensitive to reversion (particularly xylan, which has a high content of uronic acid). Under moist conditions, the hydrochloric acid released from the extractives is diluted and thus has much less influence on the degradation of the carbohydrates. The extractives then contribute to the reversion mainly through their own discoloration. The transformation of the carboxyl groups in the pulp to the hydrogen form by a sulfur dioxide treatment usually increases the brightness stability in a moist atmosphere and decreases it under dry conditions. Our results also strongly indicate that the brightness reversion is highly dependent on the degree of chlorination of residual lignin.
Analysis of the α, β, and γ relaxations in polychlorotrifluoroethylene and polyethylene: Dielectric and mechanical properties
Authors: Hoffman John D. , Williams G. , Passaglia E.
Published: June 2010

Theoretical models for the ac and γe relaxation effects found in chain‐folded polymer crystals (single crystal mats and bulk) are presented and compared with the available dielectric and mechanical loss data for polyethylene and polychlorotrifluoroethylene. Details of morphology and crystal structure that can be varied by crystallization and annealing procedures, e.g., roughness of chain‐folded surfaces, number of intercrystalline links and cilia, number of chain‐end defects and dislocations, and the existence of the extended‐chain phase, are brought into the discussion. The αc process, which consists of two overlapping mechanisms, is a result of motions of chain folds and reorientation (with translation) of chains in the interior. (Chain twisting also occurs for long chains.) The theory connects the data on the n‐paraffins and their polar derivatives (n‐ketones, esters, ethers) with the results on polymers: the common feature is the chain reorientation and twisting process. A new theory of chain twisting is introduced. The β relaxation is a result of reorientation of chains in a “loose” chain‐end induced defect (a vacancy row) in the polymer crystal. When the effect of chain twisting is included, the theory successfully predicts the unusually broad and asymmetric loss curve found in the polymer, and is consistent with the experimental activation energies. The β relaxation arising in the amorphous component of PCTFTC is analyzed, and its upward shift in temperature with increasing crystallinity discussed in terms of the Adam‐Gibbs theory of relaxation in the glassy state. The γa amorphous relaxation, and the δ relaxation which is found at cryogenic temperatures, are also discussed.
Elastic moduli of the crystal lattices of polymers
Authors: Satcurada Ichiro , Ito Taisuke , Nakamae Katsuhiko
Published: June 2010

Elastic moduli of the crystalline regions in high polymers have been studied. Oriented specimens were used throughout. Lattice strains were measured by an x‐ray technique in the direction of the fiber axis as well as in that perpendicular to the fiber axis. The moduli for both directions were calculated on the basis of the assumption that the stress is homogeneous within a specimen held under a load. Remits obtained for various kinds of polymers were discussed in terms of the crystal structures of the polymers, pan icularly the skeleton conformation and the cross‐sectional bulkiness of the chain molecule in the crystal. It was shown that the moduli in the direction of the fiber axis are widely different depending upon the polymer. They vary from 240 × 104 kg./cm.2 for polyethylene to 4.1 × 104 kg./cm.2 for isotactic poly (vinyl tert‐butyl ether). In the direction perpendicular to the fiber axis, the moduli were shown to take values within a narrow range of magnitude, 3–9 × 104 kg./cm.2. Some of these moduli were compared with the calculated values reported by several authors. To find experimental support for the assumption of the homogeneous stress, measurements were made by using several oriented specimens of different fine textural structures. Inherent values of the lattice moduli were obtained, regardless of the specimens used, which gives a strong support for the assumption.
Mechanical properties of polyethylene crystals. II. Deformation process of spherulite
Authors: Kobayashi Keinosuke , Nagasawa Toshio
Published: June 2010

Optical and electron microscopy of the plastic deformation process of polyethylene spherulitic film revealed the variation of the process with the temperature. Even within a single spherulite the mode of deformation differs with the relative position in the overall deformation; hence it is hard to represent with a simple affine model. The morphological change can be classified by dividing a spherulite into a few zones by conical boundaries which incline 45° to the direction of stretching and pass the center of the spherulite. At 20°C, the unfolding of molecules takes place in two sectors; the concentric extinction patterns are disturbed, probably due to rotation or bending of lamellae. At 95°C., the necking or the unfolding of molecules is not detected in any sector but the deformation with the slip between or within lamellae occurs preferentially in two side sectors. The anisotropic parameters corresponding to the tensile and shear compliances of simple lamellar structures are estimated from mechanical properties of tubular extruded film in which lamellae pile up along the machine direction. Applying these values of parameters to the structure model of spherulite, the mechanism of its deformation is analyzed. One of these parameters which relates to shear deformation inducing the “slip” between or within lamellae is most sensitive to temperature and varies widely with the irradiation dose (number of crosslinkings).
Temperature dependence of polymer viscosity. The influence of polymer composition
Authors: Porter Roger S. , Johnson Julian F.
Published: June 2010

The change of viscosity with temperature has been reported in the literature for a variety of linear, amorphous polymers. These data in terms of the flow activation energy, E*, indicate a wide variation among polymers with each exhibiting an essentially constant and characteristic E* at high temperature and high polymer molecular weight. These characteristic values of E* have been evaluated in terms of chemical composition and structure of individual polymer coils. The value of E* increases as a regular function of the molar volume of pendant groups along the polymer chain. More generally, a relation is shown between E* and the steric or conformational factor σ. For polyolefins, E* also increases regularly with the molar volume per monomer unit and with the mean‐square displacement length per chain unit.
Thermomechanical Behavior of Poly(ethylene Glycol Methacrylate) and Poly(diethylene Glycol Methacrylate)
Authors: Ilavský M. , Slonlmskii G. L. , Janáček J.
Published: June 2010

The influence of the length of side groups on the thermomechanical behavior of poly‐(ethylene glycol methacrylate), poly(diethylene glycol methacrylate), and their copolymers was studied. It was found that the hydroxyl endgroups increase the viseosity of these polymers compared to poly(propyl methacrylate) and poly(hexyl methacrylate); the increasing length of the side chains lowers the differences between the mechanical behavior of the poly(alkyl methacrylates) and poly(glycol methacrylates). The thermomechanical curves are sufficiently sensitive to determination of the fundamental mechanical characteristies of network polymers with very small differences of network density. A relation was obtained between the physical degree of crosslinking of poly‐(ethylene glycol methacrylate) and poly(diethylene glycol methacrylate) and the content of the crosslinking agent based on thermomechanical measurements, and the assumption has been expressed, that the physical degree of crosslinking can be partly influenced by the supermolecular structure of the polymers.
Intcractions of Macroradicals in Polyethylene‐Polypropylene Blends
Authors: Bartoň J. , Lazár M.
Published: June 2010

Transfer reactions of primary radicals formed by decomposition of dicumyl peroxide in atactic polypropylene–polyethylene blends give rise to the corresponding macroradicals. A mutual recombination of polypropylene and of polyethylene macroradicals leads to the formation of hybrid copolymer. From the values obtained experimentally it follows that the total crosslinking efficiencyE of the blend (defined as a number of total crosslinks formed per mole of dicumyl peroxide decomposed) depends on the concentration of atactic polypropylene in the blend and not on the concentration of dicumyl peroxide. The decrease in the total crosslinking efficiency of the blend is attributed to scission reactions of polypropylene macroradicals. On the basis of kinetic analysis of the crosslinking process, relations expressing the dependence of the total and interpolymer crosslinking efficiencies of the blend (the latter defined as the number of crosslinks between polypropylene and polyethylene macromolecules per mole of dicumyl peroxide decomposed) on the concentration of polypropylene and polyethylene monomer units in the blend were derived. The calculated course of interpolymer crosslinking efficiency of blend is in good agreement with the values of the interpolymer crosslinking efficiency E' for the blends determined from the concentration of polypropylene bound in the crosslinked blends. For the ratio of the rate constants of transfer to polypropylene and polyethylene we obtained a value k3/k2 = 2.3. The influence of the microheterogeneity of blends on the relations derived is discussed briefly.
Anionische Kopolymerisation einiger cyklischer Polysiloxane
Authors: Jelínek M. , Laita Z. , Kučera M.
Published: June 2010

The anionic copolymerization of some cyclic polysiloxanes catalyzed by strong bases was studied. Copolymerizations were carried out with the use of dodecamethylcyclohexasiloxane and tetradecamethylcycloheptasiloxane as M1 and heptamethylvinyl‐cyclotetrasiloxane and tetramethyltetravinylcyclotetrasiloxane as M2. LiOH, NaOH, and KOH were used as catalysts. The Mayo and Lewis method was applied in evaluating the copolymerization experiments. The values of the monomer reactivity ratios r1 and r2 obtained imply that changes in temperature do not practically affect the entry of cyclic polysiloxanes into the copolymer chain. On the other hand, copolymerization is strongly influenced by the activity of the catalyst. The character of the metal gegenion is shown in the reaction of the catalyst with the monomer in the first elementary step where it affects the equilibrium of the formation of the transition complex. It has presumably no effect on the second elementary step, i.e., the transformation and linearization of the cyclic part of the complex. The electronegative effect of the vinyl substitution on the Si atom of the cyclic tetramer results in an increased electropositivity of Si in the siloxane unit of the monomer and a decresaed electron density on oxygen of the silanolate group. As a result of these electron effects tetramethyltetravinylcyclo‐tetrasiloxane and heptamethylvinylcyclotetrasiloxane are more reactive as monomers than octamethylcyclotetrasiloxane.
Changes of Radicals in the Poly(methyl Methacrylate)—Polystyrene Systems
Authors: Lazár M. , Szǒs F.
Published: June 2010

The reactions of macroradicals produced by mechanical destruction in the systems poly (methyl methacrylate)‐polystyrene have been studied by following changes of the ESR spectra. The parent polymers were random copolymers, the mixtures of homopolymers, and graft and block copolymers with various ratios of styrene and methyl methacrylate. The transfer constants as well as the termination constants for the macroradicals have been determined. The mechanism of the transfer reactions and the importance of the chemical nature of the polymeric matrix in the decay of macroradicals are discussed.
Determination of Dispersion Characteristics of Polychloroprene Latices by Electron Microscopy and Soap Sorption Methods
Authors: Pelzbauer Z. , Hynková V. , Bezděk M. , Hrabák F.
Published: June 2010

To estimate the dispersion characteristics of polychloroprene latices, two independent methods, electron microscopy and soap sorption, were used. Within the framework of microscopic determination, agreement was demonstrated between the calculation and bromination methods. From the comparison of electron microscopy with sorption, a new value, 48.7 A.2, was assessed for the active surface of the potassium laurate molecule on the surface of latex particles. The dispersion characteristics of 19 latices were used to calculate the conversion factors between different mean particle sizes dependent on their polydispersities.
Kinelic Study of Thermal Dehydrochlorination of Poly (vinyl Chloride) in the Presence of Oxygen. Part II. Correlations of Derived Equations with Experimental Results
Authors: Valko L.
Published: June 2010

A correlation of experimental results with the equation for τ(t) derived in the first part of this study has been carried out. From the results it is evident the equation for η(t) expresses the true course of the thermal dehydrochlorination of PVC in oxygen at any temperature. It has been found that the elimination of HCl and the cleavage of C—C bonds represent a monomolecular stochastic process. The course of the kinetic curves of the first‐order reaction is changed by the influence of the dissipative factors on the asymmetrical “S” curves. From the distribution function of the bonds it appears that the bonds of the same type in the polymer chain are not equivalent in respect to the energy, and they are characterized by a “predissociated state.” From the value of the frequency factor (104 sec.−1) it can be assumed that the elimination of hydrogen chloride represents a first‐order reaction of nonadiabatic character. The rate of elimination of HC1 is not only caused by the interaction of oxygen with the double bonds but also by the number of cleft C—C bonds autocatalytically influenced. From the activation energy of scission the C—C bonds (57 kcal./mole it can be assumed that there is question of predominantly simple C—C bonds.
Photodegradation of cis‐1,4‐polyisoprene in solution sensitized by the addition of nitroso compounds in the presence of visible light
Authors: Rabek Jan F.
Published: June 2010

It was found that apart from chloronitroso compounds bromonitroso and nitronitroso compounds also sensitize the photodegradation by visible light of cis‐1,4‐polyisoprene in solution. The investigation of the kinetics of the relative viscosity decrease in solutions containing chloronitroso compounds and stable free radicals, e.g., α, α‐diphenyl‐β‐picryl hydrazyl (DPPH), di(4‐methoxyphenylo)‐N‐oxide, 2,2,4‐trimethyl‐6‐ethoxy‐1,2‐dihydroquinolin‐N‐oxide, shows that the addition of stable radicals does not prevent the photochemical reaction, but merely slows down its rate. The present investigation of the photodegradation mechanism of cis‐1,4‐polyisoprene in solution, induced by the addition of chloronitroso compounds, excludes the possibility of a direct transfer of light energy over the donor‐acceptor complex, and shows that the degradation reaction is due to free radicals formed by the decomposition of the sensitizing agent.
Determination of molecular weight distribution from osmolically measured “permeation”
Authors: Hoffmann M. , Uxbehend M.
Published: June 2010

With a quick‐acting osmometer it can be shown that in an osmotic experiment the diffusion of dissolved molecules through the membrane follows the well‐known diffusion equations. On paper intended for probability curves the dependence of the osmotic pressure on time can be represented by a straight line whose inclination, when the degree of swelling and thickness of the membrane are known, supplies the diffusion constant of the dissolved molecules in the membrane. These diffusion coefficients depend exponentially on the amount of swelling undergone by the membrane and the molecular weight of the dissolved substance. If the dissolved material is not unimolecular, a straight line is no longer obtained on paper intended for probability curves. A tangent is placed on the curve at a low time value and shifted until it has a definite ordinate value at t = ∞. The inclination of the tangent supplies the diffusion constant, whereas the quotient of the ordinates of the shifted and unshifted tangents at the point of contact is equivalent to the quotient of the total pressure and the partial pressure of the fraction. The time‐dependent partial pressure is then subtracted from the total pressure and the diffusion constant and partial pressure of the next fraction are calculated from the dependence of the residual pressure on time. Calibration measurements are carried out to find the dependence of the diffusion constants on molecular weight and in this way the molecular weights of the fractions and‐with their partial pressures‐their concentrations are determined. The partial pressures of rapidly diffusing molecules must be corrected by means of the Staverman coefficients, which can be calculated from the diffusion constants and molecular weights of the fractions and of the solvent. The method is particularly suitable for determining the low‐molecular portion of the molecular weight distribution and is insensitive to differences in the chemical nature of the dissolved molecules.
Über die anionische polymerisation α,β‐ungesältigler aldehyde. 33. Mill, über polymere acroleine
Authors: Schulz Rolf C. , Wegner Gerhard , Kern Werner
Published: June 2010

Acrolein was polymerized by anionic catalysts in bulk and in solution in the temperature range from −78 to +20°C. Effective catalysts were aliphatic and aromatic tert‐phosphines, triethylamine, alkali borohydrides, naphthyllithium, sodium naphthalene, alkali cyanides, and alkali thiocyanates. The structure of the polymers was investigated by means of physical and chemical methods. It was shown that the polyacroleins obtained with sodium cyanide in tetrahydrofuran or toluene have a uniform structure, containing only the repeating unit…—CH—O—…—CH=CH2 They are easily soluble in many organic solvents and reveal high thermal stability. In addition to acrolein the following α,β‐unsaturated aldehydes have been polymerized: methacrolein, crotonaldehyde, and propionaldehyde. With the above‐mentioned initiators they form polymers composed of several different structural units. Substitution in a‐positiou is of minor importance than substitution in α‐position with respect to the arrangement of the structural units. The polymerization activity decreases in the order acrolein > methacrolein > crotonaldehyde > propiolaldehyde.
Grafting efficiency of atactic polypropylene
Authors: Pavlinec J. , Lazár M. , Maňásek Z.
Published: June 2010

The changes of grafting efficiency of atactic polypropylene in grafting with methyl methaerylate and styrene, initiated by low molecular weight peroxides and peroxides of polypropylene, have been investigated. The assumption that the grafting efficiency of atactic polypropylene increases with an increase in temperature, monomer concentration in the initial mixture, and with the increase of molecular weight of the initial polymer was confirmed. It was also found that to reach high grafting efficiency of the basic polymer, it is necessary to select a reaction medium with maximum compatibility of the components of the system. The average number of grafted branches was determined by means of grafting efficiency of the polymer and by using Poisson's equation of distribution probability of this phenomenon.
The role of oxygen in solid‐state polymerization. I. Acrylamide and its solid solutions
Authors: Adler George
Published: June 2010

It has been shown that the presence of oxygen has little effect on the ESR spectrum of acrylamide. On the other hand, the spectrum of propionamide is markedly changed and shows sharply increased decay rates with oxygen. The behavior of solid solutions of the two is intermediate and depends on the relative concentrations of the two materials. The polymerization is markedly decreased in the solid solutions when oxygen is present. The polymerization data are thus consistent with those derived from the ESR spectra. These effects are interpreted in terms of the crystal structure of the materials and the polymerization mechanism.
A physicochemical study of poly(vinyl chloride) in solution
Authors: Kratochvíl P. , Petrus V. , Munk P. , Bohdanecký M. , Šolc K.
Published: June 2010

This paper summarizes results obtained by studying solutions of poly (vinyl chloride) in various solvents by light‐scattering, sedimentation analysis, streaming birefringence, viscometry, and osmometry. Determination of certain molecular parameters (molecular weight, dimensions of maeromolecules, and optical anisotropy of segments) is described and attention is paid to the complications which arise from the presence of supermolecular structures occurring in the solutions of poly(vinyl) chloride even in good solvents. Some conditions are given for the occurrence of the sepermolecular structures in thermodynamically good, as well as poor solvents (both single and mixed), and the structures are partially characterized. The presence of supermolecular structures makes it impossible to determine directly certain parameters, in particular, molecular dimensions.