bluuebunny/crossref_metadata_2025 huggingface dataset:
Phenotypic and genomic responses to titanium dioxide and cerium oxide nanoparticles in Arabidopsis germinants
Authors: Tumburu Laxminath , Andersen Christian P. , Rygiewicz Paul T. , Reichman Jay R.
Published: September 2014

The effects of exposure to nanoparticles of titanium dioxide (nano-titanium) and cerium oxide (nano-cerium) on gene expression and growth in Arabidopsis thaliana germinants were studied by using microarrays and quantitative real-time polymerase chain reaction (qPCR), and by evaluating germinant phenotypic plasticity. Exposure to 12 d of either nano-titania or nano-ceria altered the regulation of 204 and 142 genes, respectively. Genes induced by the nanoparticles mainly include ontology groups annotated as stimuli responsive, including both abiotic (oxidative stress, salt stress, water transport) and biotic (respiratory burst as a defense against pathogens) stimuli. Further analysis of the differentially expressed genes indicates that both nanoparticles affected a range of metabolic processes (deoxyribonucleic acid [DNA] metabolism, hormone metabolism, tetrapyrrole synthesis, and photosynthesis). Individual exposures to the nanoparticles increased percentages of seeds with emergent radicles, early development of hypocotyls and cotyledons, and those with fully grown leaves. Although there were distinct differences between the nanoparticles in their affect on molecular mechanisms attributable to enhancing germinant growth, both particles altered similar suites of genes related to various pathways and processes related to enhanced growth. Environ Toxicol Chem 2015;34:70–83. Published 2014 Wiley Periodicals Inc. on behalf of SETAC. This article is a US government work and, as such, is in the public domain in the United States of America.
Qualitatively different coding of symbolic and nonsymbolic numbers in the human brain
Authors: Lyons Ian M. , Ansari Daniel , Beilock Sian L.
Published: September 2014

Are symbolic and nonsymbolic numbers coded differently in the brain? Neuronal data indicate that overlap in numerical tuning curves is a hallmark of the approximate, analogue nature of nonsymbolic number representation. Consequently, patterns of fMRI activity should be more correlated when the representational overlap between two numbers is relatively high. In bilateral intraparietal sulci (IPS), for nonsymbolic numbers, the pattern of voxelwise correlations between pairs of numbers mirrored the amount of overlap in their tuning curves under the assumption of approximate, analogue coding. In contrast, symbolic numbers showed a flat field of modest correlations more consistent with discrete, categorical representation (no systematic overlap between numbers). Directly correlating activity patterns for a given number across formats (e.g., the numeral “6” with six dots) showed no evidence of shared symbolic and nonsymbolic number‐specific representations. Overall (univariate) activity in bilateral IPS was well fit by the log of the number being processed for both nonsymbolic and symbolic numbers. IPS activity is thus sensitive to numerosity regardless of format; however, the nature in which symbolic and nonsymbolic numbers are encoded is fundamentally different. Hum Brain Mapp 36:475–488, 2015. © 2014 Wiley Periodicals, Inc.
Low serum miR‐19a expression as a novel poor prognostic indicator in multiple myeloma
Authors: Hao Mu , Zang Meirong , Wendlandt Erik , Xu Yan , An Gang , Gong Dasen , Li Fei , Qi Fang , Zhang Yanru , Yang Ye , Zhan Fenghuang , Qiu Lugui
Published: September 2014

Multiple myeloma (MM) is the second most common hematologic malignancy characterized by the clonal expansion of plasma cells. Despite continuing advances, novel biomarkers are needed for diagnosis and prognosis of MM. In our study, we characterized the diagnostic and prognostic potential of circulating microRNAs (miRNAs) in MM. Serum miRNA levels were analyzed in 108 newly diagnosed symptomatic MM patients and 56 healthy donors (HDs). Our analysis identified 95 dysregulated miRNAs in newly diagnosed MM patients. Of the 95 dysregulated miRNAs, dysregulation of miR‐19a, miR‐92a, miR‐214‐3p, miR‐135b‐5p, miR‐4254, miR‐3658 and miR‐33b was confirmed by quantitative reverse transcription PCR (RT‐qPCR). Receiver operating characteristic analysis revealed that a combination of miR‐19a and miR‐4254 can distinguish MM from HD with a sensitivity of 91.7% and specificity of 90.5%. Decreased expression of miR‐19a was positively correlated with international staging system advancement, del(13q14) and 1q21 amplification. Furthermore, downregulation of miR‐19a resulted in significantly decreased progression‐free survival (PFS) and overall survival (OS). Our analysis indicated that the poor prognostic correlation of miR‐19a expression was independent of genetic abnormalities in MM. Multivariate analysis revealed that miR‐19a was a significant predictor of shortened PFS and OS. Interestingly, although miR‐19a levels portend a poor prognosis, patients with low miR‐19a levels had an improved response to bortezomib compared to those with high miR‐19a profile. Patients with downregulated miR‐19a experienced a significantly extended survival upon bortezomib‐based therapy. These data demonstrate that the expression patterns of serum microRNAs are altered in MM, and miR‐19a levels are a valuable prognostic marker to identify high‐risk MM.
Macroeconomic Effects of Precautionary Demand for Oil
Authors: Anzuini Alessio , Pagano Patrizio , Pisani Massimiliano
Published: September 2014

We evaluate the macroeconomic effects of shocks specific to the oil market, which mainly reflect fluctuations in precautionary demand for oil driven by uncertainty about future supplies. A two‐stage identification procedure is used. First, daily changes in the futures–spot price spread proxy for precautionary demand shocks and the path of oil prices is estimated. This information is then exploited to restrict the oil price response in a vector autoregression. Impulse responses suggest that such shocks reduce output and raise prices. Historical decomposition shows that they contributed significantly to the US recessions in the 1990s and in the early 2000s, but not to the most recent slump. Copyright © 2014 John Wiley & Sons, Ltd.
Autoantibody Profiling in a Cohort of Pediatric and Adult Patients With Autoimmune Hepatitis
Authors: Villalta Danilo , Girolami Elia , Alessio Maria Grazia , Sorrentino Maria Concetta , Tampoia Marilina , Brusca Ignazio , Daves Massimo , Porcelli Brunetta , Barberio Giuseppina , Conte Mariaelisabetta , Pantarotto Lisa , Bizzaro Nicola ,   on behalf of the Study Group on Autoimmune Diseases of the Italian Society of Laboratory Medicine, Italy
Published: September 2014

Background

Autoimmune hepatitis (AIH) is a rare condition characterized by the presence of autoantibodies distinctive of type 1 AIH (AIH‐1) and type 2 AIH (AIH‐2). The aim of this study was to evaluate the autoantibody profile in a cohort of pediatric and adult AIH patients, using both indirect immunofluorescence (IIF) and a new multiplexed line‐blot assay.

Methods

Sera from 63 pediatric and 53 adult AIH patients were tested for antinuclear (ANA), antismooth muscle (SMA), anti‐liver kidney microsome 1 (anti‐LKM1), anti‐liver cytosol 1 (anti‐LC1) autoantibodies using IIF methods; for anti‐LKM1, anti‐LC1, and soluble liver antigen/liver‐pancreas (anti‐SLA/LP) autoantibodies using the line‐blot; for anti‐F‐actin autoantibodies using IIF both on VSM47 cell‐line and on rat intestinal epithelial cells.

Results

AIH‐1 was the most common type of AIH in the adult cohort (73.6%), while AIH‐2 was the most common AIH in the pediatric cohort (61.9%). Both in adult and pediatric AIH‐2 anti‐LKM1 were the prevalent autoantibodies. In pediatric AIH‐2 anti‐LC1 autoantibodies were more frequent than in adult AIH‐2 (59 vs. 28.6%), and in 35.9% of cases they were present alone. In 17 patients anti‐LC1 autoantibodies were detected only with the line‐blot assay. The levels of anti‐LKM1 and of anti‐LC1 were not different between adult and pediatric AIH, and the overall agreement between the results obtained with the two IIF methods for F‐actin detection was 98.8% (CI 95%: 94.4–99.7%).

Conclusions

The line‐blot assay showed a higher sensitivity than IIF for anti‐LC1 detection. Anti‐LKM1 and anti‐LC1 autoantibody levels are not different in adults and children. An almost perfect agreement between the two IIF methods for anti‐F‐actin detection has been observed.
Mouse calvarial defect Model: An approach for the micro‐tomographic evaluation of polymer scaffolds
Authors: Wu Xiaohong , Wang Lu , Deng Feng , Watts David C.
Published: September 2014

The ability of bone repair scaffolds to form bone is traditionally evaluated using cell culture and animal experiments. Mouse calvarial organ culture maintains the natural cell‐to‐cell and cell‐to‐matrix relationships as well as the anatomical order, and this model has been used to study the biological behavior of intramembranous bones. The aim of this study was to evaluate the potential of mouse calvarial organ culture to be used as an in vitro model to study the bone regenerative ability of bone repair polymer scaffolds. Critical size defects (CSD) were created in the parietal bones. Electrospun poly(ε‐caprolactone) scaffolds were placed into one group of defects. The remaining defects served as a control. The bones were cultured for 38 days and analyzed with μCT, phase‐contrast microscopy, dissecting microscopy, scanning electron microscopy, and energy‐dispersive X‐ray analyses. This organ culture technique is easily available and could permit researchers to quickly establish a valuable database of candidate bone repair scaffolds. Microsc. Res. Tech. 77:1037–1043, 2014. © 2014 Wiley Periodicals, Inc.
Exploring the length of the common channel of pancreaticobiliary maljunction on magnetic resonance cholangiopancreatography
Authors: Itokawa Fumihide , Kamisawa Terumi , Nakano Toshiaki , Itoi Takao , Hamada Yoshinori , Ando Hisami , Fujii Hideki , Koshinaga Tsugumichi , Yoshida Hitoshi , Tamoto Eiji , Noda Takuo , Kimura Yasutoshi , Maguchi Hiroyuki , Urushihara Naoto , Horaguchi Jun , Morotomi Yoshiki , Sato Masahito , Hanada Keiji , Tanaka Masao , Takahashi Astushi , Yamaguchi Taketo , Arai Yuuki , Horiguchi Akihiko , Igarashi Yoshinori , Inui Kazuo ,   The Committee of Diagnostic Criteria of The Japanese Study Group on Pancreaticobiliary Muljunction
Published: September 2014

Background

In the revised diagnostic criteria for pancreaticobiliary maljunction (PBM), PBM can be diagnosed from a long common channel by magnetic resonance cholangiopancreatography (MRCP). However, it is necessary to differentiate from high confluence of pancreaticobiliary ducts (HCPBD) with a relatively long common channel (≥6 mm) and effect of the sphincter in the pancreaticobiliary junction. This multicenter study aimed to explore definite value of the length of an abnormally long common channel, which enables to distinguish PBM from HCPBD on MRCP.

Methods

In 184 PBM patients and 22 HCPBD patients who were diagnosed by direct cholangiography and underwent MRCP, the length of the common channel was measured.

Results

The length of the common channel was 16.2 ± 6.9 mm on direct cholangiography and 13.9 ± 6.2 mm on MRCP in PBM patients, and 7.7 ± 1.5 mm and 6.6 ± 1.4 mm in HCPBD patients. The optimal cut off value of the length of the common channel to distinguish PBM from HCPBD was identified to be 9 mm.

Conclusions

Pancreaticobiliary maljunction can be diagnosed from an abnormally long common channel on MRCP, but in cases of the common channel ≤9 mm on MRCP, direct cholangiography is needed to confirm PBM.
High resolution muscle measurements provide insights into equinus contractures in patients with cerebral palsy
Authors: Mathewson Margie A. , Ward Samuel R. , Chambers Henry G. , Lieber Richard L.
Published: September 2014

Muscle contractures that occur after upper motor neuron lesion are often surgically released or lengthened. However, surgical manipulation of muscle length changes a muscle's sarcomere length (Ls), which can affect force production. To predict effects of surgery, both macro‐ (fascicle length (Lf)) and micro‐ (Ls) level structural measurements are needed. Therefore, the purpose of this study was to quantify both Ls and Lf in patients with cerebral palsy (CP) as well as typically developing (TD) children. Soleus ultrasound images were obtained from children with CP and TD children. Lf was determined and, with the joint in the same position, CP biopsies were obtained and formalin fixed, and Ls was measured by laser diffraction. Since soleus Ls values were not measurable in TD children, TD Ls values were obtained using three independent methods. While average Lf did not differ between groups (CP = 3.6 ± 1.2 cm, TD = 3.5 ± 0.9 cm; p > 0.6), Ls was dramatically longer in children with CP (4.07 ± 0.45 µm vs. TD = 2.17 ± 0.24 µm; p < 0.0001). While Lf values were similar between children with CP and TD children, this was due to highly stretched sarcomeres within the soleus muscle. Surgical manipulation of muscle‐tendon unit length will thus alter muscle sarcomere length and change force generating capacity of the muscle. © 2014 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 33:33–39, 2015.
Use of the backslopping method for accelerated and nutritionally enriched idli fermentation
Authors: Shrivastava Neha , Ananthanarayan Laxmi
Published: September 2014

BACKGROUND

Idli is a cereal–legume‐based fermented food, widely consumed in India. It is popular for its nutritional content, sour taste and appetising aroma. The fermentation time of idli batter varies from 12 to 14 h. A reduction in fermentation time of idli batter is of great significance for large‐scale idli production units since it will reduce the batch time and will lead to a greater output. Accelerated fermentation can be potentially achieved by using the backslopping method. The inoculum for backslopping was optimally fermented (12 h) idli batter, dried at room temperature.

RESULTS

Backslopping reduced the fermentation time of idli batter from the conventional 12 h to 3 h while successfully maintaining sensory attributes of the product. In the idlis prepared by backslopped expedited batter, thiamine was found to be 50% higher; while reduction of anti‐nutrients phytate (11%) and trypsin inhibitor (16%) was higher than the conventionally fermented (12 h) idli batter.

CONCLUSION

Backslopping not only accelerated idli batter fermentation but also enhanced its nutritional value. A similar process can be designed for other fermented foods, to expedite fermentation thus reducing the time requirement. © 2014 Society of Chemical Industry
Mechanics of circular breathing in wind musicians using cine magnetic resonance imaging techniques
Authors: Peng Tiffany , Phillips C. Douglas , Dyke Jonathan P. , Stewart Michael G.
Published: September 2014

Objectives/Hypothesis

To investigate the mechanics of circular breathing using cine magnetic resonance imaging (cMRI).

Study Design

Pilot study.

Methods

Eight musicians were asked to sustain a note by circular breathing while being studied inside a Siemens Trio 3T magnetic resonance imaging scanner. Subjects were imaged in the midsagittal plane using an innovative T1‐weighted cMRI. Our study population included six professionals and two experienced amateurs (two saxophonists, two trombonists, and four trumpeters). Five predetermined oropharyngeal distances were measured frame by frame. Data were analyzed for displacement and percentage change over time. Oral airway area was measured using automated bounding box techniques.

Results

All subjects were observed to complete the same series of steps characterized by 1) superior/posterior tongue displacement, 2) inferior/anterior soft palate displacement, 3) anterior tongue/soft palate displacement, 4) superior/posterior soft palate displacement, and 5) return of the tongue to baseline. Posterior oropharyngeal occlusion was demonstrated in bounding box data. Relative occlusion time was significantly longer among experienced amateurs than professionals (P = .01), with a similar trend in absolute occlusion time (P = .08). A trend toward a longer circular breathing cycle time was observed among saxophonists and trumpeters (P = .2), although the difference among trumpeters disappeared when amateurs were excluded.

Conclusions

Circular breathing has been investigated as therapy for obstructive sleep apnea. This study defines the mechanics of circular breathing for use in training—and potentially in therapy—if proven useful. We demonstrated similar mechanics across subgroups, and increased efficiency among professionals. Our findings demonstrate the feasibility and reliability of cMRI in the dynamic assessment of oropharyngeal motion.

Level of Evidence

NA Laryngoscope, 125:412–418, 2015
Post‐ovulatory aging of oocytes disrupts kinase signaling pathways and lysosome biogenesis
Authors: MCGinnis Lynda K. , Pelech Steven , Kinsey William H.
Published: September 2014

Post‐ovulatory aging of oocytes results in the progressive loss of fertilization and developmental competence. This degradation of oocyte quality has been the object of numerous investigations, primarily focused on individual signaling pathways which provide limited insight into the status of global signaling events. The purpose of the present investigation was to comprehensively assess broad patterns of signaling pathway activity during in vitro aging as an initial step in defining control points that can be targeted to prevent the reduction in oocyte quality during prolonged culture. An antibody microarray‐based phospho‐proteome analysis performed on oocytes before and after eight hours of culture revealed significant changes in the abundance or activation state of 43 proteins that function in a wide variety of protein kinase‐mediated signaling pathways. Several of the most significantly affected kinases were studied by Western blot and confocal immunofluorescence to corroborate the array results. Prolonged culture resulted in global changes in the abundance and activity of protein kinases that regulate the response to calcium, stress, and cell‐cycle control. Examination of intracellular structures revealed a previously unrecognized increase in the abundance of large autophogagic lysosomes, which correlates with changes in protein kinase pathways. These results provide insight into the stresses experienced by oocytes during culture and the diversity of responses that results from them. The observed increase in autophagy‐related activity, together with the disruptions in calcium signaling, cell‐cycle, and stress‐response pathways, have the potential to negatively impact oocyte quality by interfering with the normal sequence of biochemical changes that constitute egg activation following fertilization. Mol. Reprod. Dev. 81: 928–945, 2014. © 2014 Wiley Periodicals, Inc.
Three‐dimensional whole‐heart T2 mapping at 3T
Authors: Ding Haiyan , Fernandez‐de‐Manuel Laura , Schär Michael , Schuleri Karl H. , Halperin Henry , He Le , Zviman M. Muz , Beinart Roy , Herzka Daniel A.
Published: September 2014

Purpose

Detecting variations in myocardial water content with T2 mapping is superior to conventional T2‐weighted MRI since quantification enables direct observation of complicated pathology. Most commonly used T2 mapping techniques are limited in achievable spatial and/or temporal resolution, both of which reduce accuracy due to partial‐volume averaging and misregistration between images. The goal of this study was to validate a novel free breathing T2 mapping sequence that overcomes these limitations.

Methods

The proposed technique was made insensitive to heart rate variability through the use of a saturation prepulse to reset magnetization every heartbeat. Respiratory navigator‐gated, differentially T2‐weighted volumes were interleaved per heartbeat, guaranteeing registered images and robust voxel‐by‐voxel T2 maps. Free breathing acquisitions removed limits on spatial resolution and allowed short diastolic windows. Accuracy was quantified with simulations and phantoms.

Results

Homogeneous three‐dimensional (3D) T2 maps were obtained from normal human subjects and swine. Normal human and swine left ventricular T2 values were 42.3 ± 4.0 and 43.5 ± 4.3 ms, respectively. The T2 value for edematous myocardium obtained from a swine model of acute myocardial infarction was 59.1 ± 7.1 ms.

Conclusion

Free‐breathing accurate 3D T2 mapping is feasible and may be applicable in myocardial assessment in lieu of current clinical black blood, T2‐weighted techniques. Magn Reson Med 74:803–816, 2015. © 2014 Wiley Periodicals, Inc.
Characterization of free, restricted, and entrapped water environments in poly(N‐isopropyl acrylamide) hydrogels via1H HRMAS PFG NMRspectroscopy
Authors: Alam Todd M. , Childress Kimberly K. , Pastoor Kevin , Rice Charles V.
Published: September 2014

Different water environments in poly(N‐isopropyl acrylamide) (PNIPAAm) hydrogels are identified and characterized using1H high resolution magic angle spinning (HRMAS) nuclear magnetic resonance (NMR). Local water environments corresponding to a “free” highly mobile species, along with waters showing restricted dynamics are resolved in these swollen hydro‐gels. For photo‐initiated polymerized PNIPAAm gels, an additional entrapped water species is observed. Spin–spinR2relaxation experiments support the argument of reduced mobility in the restricted and entrapped water species. By combining pulse field gradient techniques with HRMAS NMR it is possible to directly measure the self‐diffusion rate for these different water environments. The behavior of the heterogeneous water environments through the lower critical solution temperature transition is described. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys.2014,52, 1521–1527
Crystal structure of syndiotactic polypropylene
Authors: Corradini P. , Natta G. , Ganis P. , Temussi P. A.
Published: September 2014

Double oriented fiber spectra of syndiotactic polypropylene were obtained. It was possible to redetermine with greater accuracy the unit cell constants, which are: a = 14.50, b = 5.60, c = 7.40 A. Space group: C2221. It was proved that the chain has s(2/1)2 symmetry, corresponding to a succession of internal rotation angles A2B2A2B2. The agreement between experimental and calculated intensities on the hkl layers with l = 0, 1, 2, 3 up to the lowest observed Bragg distance (about 2 A.) is good for the packing model proposed. The structural results are briefly discussed.
Polymerization of propylene to syndiotactic polymer. II. Behavior of the catalytic system VCl4–Al(C2H5)2Cl
Authors: Zambelli A. , Natta G. , Pasquon I. , Signorini R.
Published: September 2014

Some data on the kinetic behavior of the catalytic system VCl4–Al(C2H5)2Cl, which is stereospecific (at low temperatures) for the polymerization of propylene to syndiotactic polymer, are reported here. The effect was studied of the reaction time and of the concentration of VCl4, of Al(C2H5)2Cl, and of the monomer on the polymerization rate, on the molecular weight, and on the index of syndiotacticity of the polymers obtained. The data reported are discussed on the basis of the hypotheses previously put forth about the nature of the catalytic complexes and the polymerization mechanism.
Some aspects of the polymerization mechanism of α‐olefins to isotactic polymers
Authors: Pasquon I. , Natta G. , Zambelli A. , Marinangeli A. , Surico A.
Published: September 2014

Data on the behavior of different heterogeneous catalyst systems in the polymerization of α‐olefins to isotactic polymer are reported and compared. The effect of substituents on the kinetic behavior of the catalyst complexes, which in the different systems yield polymeric chains having comparable steric regularities, was investigated. Moreover, hypotheses are put forth on the factors influencing the stereospecificity of the catalyst systems studied.
On some regularities of the polycoordination reaction
Authors: Vinogradova S. V. , Korshak V. V. , Vinogradov M. G.
Published: September 2014

On the interaction of bis(aeetoacetyl)phenyl ether, 1,2‐bis(acetoacetyl)diphenyl ethane and sebacyl diacetone with beryllium acetylacetonate coordination polymers of high molecular weight have been synthesized. Kinetics of polycoordination of bis(acetoacetyl)phenyl ether with beryllium acetylacetonate in solution at 55–85°C. have been studied. The reaction is reversible and proceeds as a bimolecular process with activation energy in dimethylformamide at 25 kcal./mole. It was established that there are exchange reactions proceeding extraordinary easily (in solution already at room temperature) between units of coordination polymers. In concentrated solutions there occurs chiefly an intermolecular interaction between macromolecules of different length. In diluted solutions under influence of entropy factor principally intramolecular exchange reactions take place leading to degradation of the polymer with formation of macrocyclic products. Degradation of the coordination polymer of sebacyl diacetone with the beryllium resulted in the formation of a macrocyclic monomeric complex of sebacyl diacetone with beryllium with fair yield. The influence of solution concentration and temperature on the equilibrium linear polymer ⇌ macrocycles have been considered.
γ‐radiation‐initiated polymerization of N‐vinylsuccinimide in the liquid and solid states
Authors: Hardy Gy. , Varga J. , Nagy G. , Cser F. , Erö J.
Published: September 2014

The γ‐radiation‐initiated polymerization of NVSI in both the liquid and solid phases proceeds according to a radical mechanism. Polymerization rate and molecular weight of the product are higher in the liquid phase than in the solid phase. A number of features characteristic of monomers polymerizing according to accelerated kinetics can be demonstrated on the model of NVSI, which in many respects behaves similarly to acrylic amide. Kinetical data, the polymer formed and the accelerating effect of inert additives, the amorphous structure of the polymer formed, the high activation energy of polymerization, as well as the isotropic ESR spectrum of the assumed growing radical, are all findings which prove that in the course of growth the monomer molecule must leave the crystal lattice, that is, that the geometry of the crystal lattice does not favor polymerization.
The effect of chemical structure on thermal, hydrolytic, and solvent resistance of polyurethane films
Authors: Reegen S. L. , Frisch K. C.
Published: September 2014

A study of the resistance of polyurethane films to various swelling and degrading environments was carried out. Physical properties of the resulting polymers were correlated with chemical variations in the polyether and isocyanate structures. Thermal resistance was determined by various techniques, including differential thermal analysis, thermogravimetric analysis, and heat aging. High crosslink density and the use of polyisocyanates of high aromatic content resulted in increased thermal stability. Resistance to moisture at high temperatures was also found to increase with crosslink density; it was influenced by the type of polyol and isocyanate used in the urethane reaction. Solvent resistance of polyurethane structures increased at higher crosslink densities, appeared to be unaffected by the type of aromatic diisocyanate, and was reduced with the use of a large excess of isocyanate. The ultraviolet resistance of films prepared from various isocyanates decreased in the order: tolylene diisocyanate (TDI) > polyphenyl polymethylene polyisocyanate (PAPI) > xylylene diisocyanate (XDI).
The calculation of average functions of local conformations for a non‐interacting copolymer system with neighbor interactions
Authors: Allegua G.
Published: September 2014

In the present paper a new treatment is given for the calculation of average conformations over a non‐interacting copolymer system, where two kinds of monomer units are present. It is based on the calculation of the arithmetical average partition function over a properly restricted class of distributions of A and B units. This method permits in principle any required degree of approximation and also may be extended to copolymer systems with three or more types of monomer units. Moreover, it has the advantage that any average of conformational functions may be calculated in a way which is formally analogous to the matrix method given by Lifson in the case of homopolymers.
Purification du trans‐Pentadiène‐1,3 par Fusion de Zones à Basse Température
Authors: Kieffer R.
Published: September 2014

Les méthodes classiques de purification tel que la distillation, la sulfonation, la condensation avec l'anhydride maléique, ne nous permettent pas d'obtenir du trans‐pentadiène‐1,3 à plus de 99% de pureté. Nous avons appliqué la purification par fusion de zone à ce produit ce qui nous a permis d'obtenir une pureté de 99,90%. L'appareil utilisé, d'un fonctionnement entièrement automatique, nous a permis de travailler à des températures très basses qui n'avaient jamais été utilisées jusqu'à présent. L'appareil comporte une circulation de propane préalablement refroidi dans l'air liquide pour la réalisation des basses températures. Le contrôle de la pureté a été effectué par analyse thermique suivant la méthode de Skau, que nous avons adapté aux basses températures. Elle permet des mesures précises à 0,01% en n'utilisant que 1 g de substance alors que la méthode de Rossini en demande 50 g.
Gelation of concentrated polymer solutions. I. Structural changes accompanying the isothermal gelation of polyacrylonitrile solutions
Authors: Łabudzińska Anna , Wasiak Andrzej , Ziabicki Andrzej
Published: September 2014

Isothermal gelation of concentrated solutions of polyacrylonitrile and acrylonitrile–methyl methacrylate copolymer in water containing dimethylformamide was followed with viscosity, light scattering, and wide‐angle, x‐ray diffraction techniques. It was found that in some cases gelation is accompanied by a strong change of light‐scattering characteristics, indicating heterogeneities in the range above 100 ÷ 200 A. In some cases also appear x‐ray diffraction rings in the gels, characteristic of crystalline order. However, all these changes were found to be not specific for the gelation process, and are believed to be connected with other processes (e.g., polymer precipitation) which accompany the gelation. It was also found that the structure of gels (as determined by light‐scattering and x‐ray diffraction) is determined as well by the composition and temperature of the system as by its thermal history.
Hydrodynamic properties of dilute polymer solutions in a general velocity field
Authors: Takserman‐Krozer R.
Published: September 2014

The hydrodynamic behavior of flexible chain macromolecules in dilute solution subjected to flow in a general velocity field is analyzed. A system of subchains with internal viscosity is used as a molecular model. On the basis of the general theory, the dependence of average deformation, orientation, and polarization characteristics of solutions upon the velocity gradient components, the internal viscosity parameter ρ, and time, is discussed for some simple and composite velocity fields.
Conductivité Electronique et Propriétés Chimiques de Polyanilines Oligomères
Authors: Jozefowicz M. , Yu L. T. , Belorgey G. , Buvet R.
Published: September 2014

Les produits obtenus à partir d'une méthode simple de préparation des éméraldines out été étudiés en ce qui concerne leurs propriétés d'acidité, d'oxydo‐réduction et de formation de complexes: (1) l'analyse des courbes de neutralisation de suspensions aqueuses d'éméraldines par des bases fortes a permis d'établir que ces composés avaient deux comportements acides différents respectivement fort et faible; (2) l'analyse des caractéristiques quantitatives de ces courbes permet de conclure à la formation de complexes avec les anions sulfate, chlorure et formiate; (3) l'action de divers couples oxydants et réducteurs sur les éméraldines en suspension aqueuse ou en solution colloïdale acétique a été étudiée. Des paramètres définissant les bilans des réactions d'oxydor‐éduction caractéristiques des matériaux étudiés ont été déterminés. Cette étude des propriétés chimiques des produits d'oxydation de l'aniline a permis de préciser les conditions d'obtention de différents dérivés appartenant à la famille des polyanilines. L'étude de la conductivité d'une classe de complexes des éméraldines (sulfates) montre qu'elle est électronique et reproductible. Elle est fonction des paramètres définissant l'état d'hydratation et l'état acide–base des différents dérivés. Elle est très élevée pour un matériau organique, et varie de 10 à 10−4 ohm−1 cm−1 selon la valeur de ces paramètres.
Vergleichende Untersuchungen der Pfropfung von Styrol auf Polyäthylen durch verschiedene Initiierungsmethoden
Authors: Czvikovszky T. , Dobó J.
Published: September 2014

Es wurde die Pfropf‐Kopolymerisation von Styrol auf Polyäthylen mittels Benzoylperoxyd, Azoisobuttersäurenitril, Lauroylperoxyd, Dikumylperoxyd, Cyklohexanonhydroperoxyd, Furoylperoxyd, Bromfuroylperoxyd und Nikotinoylperoxyd untersucht und mit der spontanen Pfropfung und der Pfropfung durch gleichzeitige Bestrahlung verglichen. Die vier erstgenannten Initiatoren sind in der Pfropfung fast ebenso effektiv, wie die spontane (thermische) Initiierung, die drei letzten geben hingegen praktisch keine Pfropfung. Es wird geschlossen, dass die Pfropfung durch eine Übertragungsreaktion vom Primärradikal auf das Polyäthylen zustande kommt und dass die wachsenden Polystyrol‐Radikale keine Übertragung auf das Polyäthylen aufweisen. Die Pfropfung durch gleichzeitige Bestrahlung hat eine höhere Effektivität, was dadurch zu erklären ist, dass in diesem Fall ein Teil der Radikale nicht in der Monomerenphase, sondern unmittelbar auf dem Polyäthylen‐Skelett entsteht. In einzelnen Fällen scheint ein Kettenabbruch durch Primärradikale die Pfropfgeschwindigkeit zu gebrenzen.
Yielding of glassy polymers: Volume effects
Authors: Whitney W. , Andrews R. D.
Published: September 2014

A yield criterion is constructed for glassy polymers from results of constant strain‐rate tests in different stress fields. A significant effect of hydrostatic pressure (or volume change) on the yield stress of polystyrene was found. Direct dilatometric measurements were made on polystyrene, poly(methyl methacrylate), polycarbonate, and poly(vinyl formal) samples subjected to uniaxial compression. Both a volume contraction proportional to stress (Poisson's ratio effect) and a volume expansion, which depends on the extent and the history of plastic yielding, were observed. These results are discussed qualitatively in terms of structural models for the glassy state of amorphous polymers.
Synthetische Lineare Polymere. XXIII. Vergleich von Gewissen Spezifischen Grenzwerten Linearer und Cyklischer Polymerhomologer Reihen
Authors: Gêzy I.
Published: September 2014

Examination of the equation for polymer‐homologous compounds, φ8p = a/M + b, which can be also deduced and where φ8p = any specific property which can be derived from the additive one; M = molecular weight; a = constant, implicitly characteristic of the end group; b = constant, explicitly characteristic of the repeating units, showed that this equation can be extended to cyclic polymer‐homologous compounds. In this case the constant a, if its value is not equal to 0, cannot be interpreted and can only be considered as a mere empirical constant. The constant b is characteristic of the repeating units and, with the exception of the specific mean‐square dipole moment of poly(dimethyl siloxanes), can similarly be interpreted or calculated as with linear polymer‐homologous compounds. In the latter case the value b—referring to the cyclic polymer‐homologous series—differs from that of the linear. With reference to the dipole moment, in the case of poly(dimethyl siloxanes), the conclusion can be drawn that the free rotation of the repeating unit within the ring is more hindered than that of the linear one.
Copolymérisation Radiochimique du Styrène avec l'Acrylonitrile dans des Milieux de Nature Différente
Authors: Chapiro Adolphe , Anna‐Maria  , Jendrychowska‐Bonamour
Published: September 2014

La copolymérisation radiochimique du styrène (St) avec l'acrylonitrile (AN) a été étudiée: (a) en masse à 0°, 20° et 50°; (b) en solution dans le diméthylformamide (DMF) à −78°; (c) dans un mélange d'adipates de diisodécyle formant un gel à −78°. (a) La copolymérisation en masse a été étudiée dans un grand domaine d'intensités de rayonnement. L'exposant de l'intensité était de 0,5 sauf pour les mélanges riches en AN où la précipitation du polymère perturbait la cinétique de la réaction. Les variations des vitesses et des compositions des copolymères obtenus en fonction de la composition du mélange initial des monomères suivaient la relation que l'on obtient avec les méthodes d'amorçage radicalaire classiques. Cependant à 0° les copolymères obtenus étaient enrichis en styrène ce qui indique la contribution d'un mécanisme cationique. (b) Dans les solutions des deux monomères dans le DMF on a pu séparer apres irradiation à −78° un polymère précipitable par le méthanol qui s'est révélé être du polyacrylonitrile pratiquement pur et un résidu cireux qui renfermait à la fois du St et du AN. Il semble donc que l'on observe simultanémént dans ce système une polymérisation anionique conduisant au PAN et une réaction radicalaire donnant nasisance à des copolymères de masse moléculaire peu élevée. (c) Dans le milieu rigide formé par les mélanges des monomères avec le diadipate d'isodécyle à −78° la réaction était assez rapide. La cinétique de cette copolymérisation était analogue à celle de la réaction en masse observée aux températures plus élevées. La composition des copolymères obtenus confirme le mécanisme radicalaire de ce processus. La vitesse appréciable de cette réaction, et le fait que les hauts polymères étaient obtenus malgré la température très basse, étaient interprétés en admettant que la réaction de terminaison des chaînes était très lente dans ce milieu.
Polymérisations et Copolymérisations Radiochimiques dans des Milieux Vitreux à Basse Température
Authors: Chapiro Adolphe , Roussel Daniel
Published: September 2014

On a montré précédemment que le méthacrylate de méthyle (MMA) qui ne se polymérise pas à l'état cristallisé, peut être polymérisé lorsqu'il est irradié à basse température en dispersion solide dans l'huile de paraffine. Cette réaction a maintenant été étendue à d'autres monomères vinyliques: chlorure de vinyle (ClV), acrylonitrile (AN) et styrène (St) et à d'autres milieux vitreux. Les irradiations étaient effectuées avec des rayons γ du cobalt‐60 à −78° et à −196°. Le méthacrylate de méthyle a été irradié en solution solide dans deux mélanges de paraffines normales qui cristallisaient à basse température. La polymérisation était très faible. Au contraire, dans un mélange d'adipates de diisodécyle qui formait un gel à −78° la réaction était très rapide, plus rapide que dans l'huile de paraffine. Les masses moléculaires des polymères formés étaient elles aussi plus élevées. Le ClV était également polymérisé dans ces deux milieux; à −78° la vitesse était plus élevée dans l'huile de paraffine que dans le mélange d'adipates. Le styrène était irradié dans l'huile de paraffine et l'acrylonitrile dans le mélange d'adipates. La réaction était semblable à celle observée pour les autres monomères. La vitesse était maximale pour les solutions très diluées. Les copolymérisations des mélanges St + MAM, St + AN, et AN + MAM ont été effectuées dans les mêmes milieux. La cinétique de ces réactions et la composition des copolymères étaient semblables à celles observées dans les copolymérisations radicalaires correspondantes. La structure de ces mélanges solides à basse température a été examinée aux rayons X, au microscope polarisant et au microscope électronique. Les résultats ont mis en évidence une séparation en deux phases. La cinétique de la polymérisation observée a pu être expliquée sur la base de cette étude.
Mécanisme de l'Amorçage de la Polymérisation des Épisulfures par le Naphtalène‐Sodium
Authors: Boileau Sylvie , Champetier Georges , Sigwalt Pierre
Published: September 2014

La réaction d'amorçage des sulfures d'éthylène et de propylène par le naphtalène sodium, en solution diluée dans le tétrahydrofuranne, a été étudiée à −70 et à 0°C. Les polymères ne renferment pas de groupements naphtaléniques ou dihydronaphtaléniques dans la chaîne. La préparation de solutions de naphtalène sodium pur exempt de naphtalène a permis un dosage comparatif du naphtalène‐sodium servant à l'amorçage et du naphtalène libre présent après amorçage. Leurs concentrations sont égales, et le seul mécanisme d'amorçage compatible avec ces résultats et avec les masses moléculaires des polymères consiste en un transfert électronique au monomère, suivi d'une dimérisation des ions radicaux formés.
Ordnungsvorgänge bei der Gelbildung aus Cellulosexanthogenatsolen
Authors: Gröbe A. , Purz H.‐J. , Maron R.
Published: September 2014

Gegenstand der Untersuchungen waren die bei der Gelbildung aus Cellulosexanthogenatsolen auftretenden Strukturen und deren Entstehungsmechanismus. Es konnte gezeigt werden, dass bei der Verwendung des Polyelektrolyten Na‐Cellulosexanthogenat mit bestimmten Gegenionen eine geordnete Gelbildung auftritt, die zu spezifischen Strukturformell führen kann, wie sie bei der ionotropen Gelbildung beobachtet wurde. Die dabei auftretenden Kapillarstrukturen wurden lichtoptisch in Abhängigkeit von Versuchsparametern, wie Elektrolytkonzentration, Solkonzentration und Solzusätzen untersucht. Die Versuchsergebnisse lassen sich mit den bei der ionotropen Gelbildung diskutierten Mechanisme nerklären. Elektronenmikroskopische Untersuchungen erfolgten an Ultradünnschnitten von Gelfäden, die durch Verspinnen von Na‐Cellulosexanthogenatsolen in Elektrolytbäder verschiedener Zusammensetzung erhalten wurden. Hierbei festgestellte Netzstrukturen sind eine Folge des Vorganges der tropfigen Entmischung während der Sol‐Gelumwandlung. Netzstrukturen findet man auch an Ultradünuschnitten von Celluloseregeneratfäden aus technischer Viskose, wenn der Quellungszustand durch Gefriertrocknung oder Lösungsmittelaustausch im Faden erhalten wird. Aus den vorgelegten Ergebnissen geht hervor, dass die Struktur von Celluloseregeneratfäden durch die Sol‐Gelumwandlung bestimmt wird. Diese auftretenden Strukturformen wurden sowohl lichtmikroskopisch als auch elektronenmikroskopisch untersucht. Es wird gezeigt, dass man einen solchen Mechanismus der Strukturbildung auch bei der Herstellung technischer Viskosefäden annehmen muss.
Conformation du Polystyrène en Solution
Authors: Reiss Claude , Benoit Henri
Published: September 2014

The thermal behavior of polystyrene in dilute solution has been studied by a number of methods of physical chemistry. By ultraviolet and infrared absorption measurements and other means, it has been shown that the helical conformation ascribed to the crystalline isotactic polystyrene is preserved in solution below 50°C. but vanishes beyond 80°C. Atactic polystyrene shows similar behavior, and thus probably contains stereoregular sequences. Detailed viscosity and light scattering studies in various theta solvents are presented.
Stress–birefringence properties of styrene–isoprene block copolymers
Authors: Henderson J. F. , Grundy K. H. , Fischer E.
Published: September 2014

Stress–birefringence measurements have been made on a number of styrene–isoprene block copolymers, and their mechanical properties have been interpreted in terms of their molecular structures. Essentially, the polymers consist of highly dispersed phases of polystyrene and polyisoprene and undergo elastic deformation with the polystyrene domains acting as crosslinks. Hysteresis measurements have been carried out to interpret the stress–strain behavior of the polymers in more detail and the conformational properties of films prepared with selective solvents have also been examined with similar birefringence techniques.
Cellulose ethers and esters with a low degree of substitution
Authors: Petropavlovskii G. A.
Published: September 2014

Cellulose ethers and esters with a low degree of substitution possess several new physico‐chemical properties as compared with the initial cellulose. Thus, ethers and esters with low degrees of substitution can dissolve in alkali solutions at low temperature and are more accessible to various reagents. These properties are explained by a distortion of supermolecular structure: its amorphization and the weakening of hydrogen bonding. This explanation is confirmed by x‐ray analysis and by infrared spectroscopy. X‐ray analysis of various cellulose ethers and esters with low degrees of substitution has shown that a considerable decrystallization of initial structure occurs even at the very first stages of etherification and esterification. The degree of this process depends both on the nature of the initial cellulose and on the type of the reaction (superficial, permutoid reaction). Infrared spectroscopy has shown that the substitution of a small part of hydroxyl groups in cellulose by various radicals evidently causes a new strength distribution of hydrogen bonds of the remaining hydroxyl groups. This distribution is distinguished by a greater percentage of weaker bonds.
Investigation of thermal and thermooxidative degradation of polyarylates
Authors: Rode V. V. , Rafikov S. R. , Zhuravleva I. V.
Published: September 2014

A study of aging processes of polyarylates at low degrees of conversion revealed that crosslinking predominates during both thermal and thermooxidative processes. To evaluate the degree of crosslinking during the aging of polyarylates, calculation of the density of the polymer network has been carried out for the insoluble fraction of polymers according to Flory. An increase in temperature results in a regular increase of cross‐linkages. Polymer Ph‐2, however, loses the ability to swell at a greater rate than D‐9. The effect of oxygen on the amount of crosslinking is insignificant. The molecular weight has been found to increase in the temperature range of 250–275°C., this phenomenon is a result of branching as consequence of degradation processes. An increase of the temperature to 300–350°C. results in formation of insoluble structures. At 250–350°C. both crosslinking and cleavage of the macromolecule chain occur. Formation of three‐dimensional structures has also been proved by calculation of crosslinking and cleavage probabilities. Polyarylate Ph‐2 undergoes crosslinking to a higher degree. This is due to the peculiarity of its composition, in that its side substituent contains the easily broken lactone ring. The presence of this substituent increases the probability of crosslinking; this is well confirmed by other data obtained by us.
Radiation‐induced solid‐state polymerization of a homologous series of N‐tert‐alkylacrylamides
Authors: Zurakowska‐Orszagh Janina
Published: September 2014

A study on the solid‐state polymerization of an homologous series of N‐tert‐alkylacrylamides under the action of γ‐radiation was carried out. More than twenty monomers of this series have been prepared starting from N‐sec‐isopropylacrylamide and N‐tert‐butylacrylamide to N‐tert‐tetradecylacrylamide. Some N‐arylacrylamides and N‐arylmethacrylamides were included also. For comparison the polymerization in solution of the same series of monomers induced by radiation as well as by chemical initiators was investigated. Results obtained for the series of N‐tert‐heptylacrylamides and N‐tert‐hexylacrylamides were discussed in more detail. An interesting coincidence between the reactivity of the particular isomers in the solid state and in solution was observed also for the radiation‐induced as well as chemically initiated polymerization. The comparison of melting points of both isomers series with their reactivity in the solid state shows that, in general, higher polymerization rates correspond to lower melting temperatures. The role of the symmetry and the structure of the homologous substituents on the polymerization rate was observed.