bluuebunny/crossref_metadata_2025 huggingface dataset:
Signal regulatory protein alpha (SIRPα) regulates the homeostasis of CD103+CD11b+DCs in the intestinal lamina propria
Authors: Scott Charlotte L. , Zangerle Murray Tamsin F. P. , Beckham Katherine S. H. , Douce Gillian , Mowat Allan McI.
Published: September 2014

Signal regulatory protein alpha (SIRPα/CD172a) is a conserved transmembrane protein thought to play an inhibitory role in immune function by binding the ubiquitous ligand CD47. SIRPα expression has been used to identify dendritic cell subsets across species and here we examined its expression and function on intestinal DCs in mice. Normal mucosa contains four subsets of DCs based on their expression of CD103 and CD11b and three of these express SIRPα. However, loss of SIRPα signaling in mice leads to a selective reduction in the CD103+CD11b+ subset of DCs in the small intestine, colon, and among migratory DCs in the mesenteric lymph node. In parallel, these mice have reduced numbers of TH17 cells in steady‐state intestinal mucosa, and a defective TH17 response to Citrobacter infection. Identical results were obtained in CD47KO mice. DC precursors from SIRPα mutant mice had an enhanced ability to generate CD103+CD11b+ DCs in vivo, but CD103+CD11b+ DCs from mutant mice were more prone to die by apoptosis. These data show a previously unappreciated and crucial role for SIRPα in the homeostasis of CD103+CD11b+ DCs in the intestine, as well as providing further evidence that this subset of DCs is critical for the development of mucosal TH17 responses.
Diversity‐Oriented Synthesis of Calothrixins and Ellipticines
Authors: Dethe Dattatraya H. , Murhade Ganesh M.
Published: September 2014

The divergent synthesis of calothrixins and ellipticines has been accomplished by utilising the one‐pot formation of o‐diacylarenes as a key intermediate through rearrangement of o‐hydroxy ketone monoacyl hydrazones by lead tetraacetate mediated oxidation.
Dynamics of grains falling on a sloping granular medium: application to the evolution of a talus
Authors: De Blasio Fabio Vittorio , Sæter May‐Britt
Published: September 2014

Numerous field surveys have provided quantitative information on the characteristics of talus deposits. Much less has been done to quantify the basic dynamics processes of blocks involved in talus evolution. In this work, we perform a set of experiments at the reduced scale of some metres using an inclined board covered with a loose granular medium. The complexity of the processes forming a talus is simplified by studying the interaction of only two kinds of grain sizes at a time. Grains of one class size are dropped from a fixed height onto the board covered by a layer of grains of a different class size, and their final distribution is recorded.

We find that when small grains fall on large grains, the granular abundance decreases rapidly as a function of the distance from the fall point, which is explained by the effect of multiple bouncing on the irregular surface. In contrast, large grains falling on a bed of smaller grains lose much more energy at impact. They may stop at once, or roll down slope, often reaching the whole board length; as a consequence, their abundance peaks in the fall zone and at the change of slope. Experiments also show that grains travel longer with increasing fall height and sloping angle. The results clarify in a physical manner one mechanism that might explain why large blocks are typically found in the distal part of a talus slope, while smaller blocks remain near the fall zone. Based on these and previous experiments, a schematic view of talus evolution is discussed. Copyright © 2014 John Wiley & Sons, Ltd.
Evaluation of the three-phase equilibrium method for measuring temperature dependence of internally consistent partition coefficients (KOW, KOA, and KAW) for volatile methylsiloxanes and trimethylsilanol
Authors: Xu Shihe , Kropscott Bruce
Published: September 2014

Partitioning equilibria and their temperature dependence of chemicals between different environmental media are important in determining the fate, transport, and distribution of contaminants. Unfortunately, internally consistent air/water (KAW), 1-octanol/air (KOA), and 1-octanol/water (KOW) partition coefficients, as well as information on their temperature dependence, are scarce for organosilicon compounds because of the reactivity of these compounds in water and octanol and their extreme partition coefficients. A newly published 3-phase equilibrium method was evaluated for simultaneous determination of the temperature dependence of KAW, KOA, and KOW of 5 volatile methylsiloxanes (VMS) and trimethylsilanol (TMS) in a temperature range from 4 °C to 35 °C. The measured partition coefficients at the different temperatures for any given compound, and the enthalpy and entropy changes for the corresponding partition processes, were all internally consistent, suggesting that the 3-phase equilibrium method is suitable for this type of measurement. Compared with common environmental contaminants reported in the literature, VMS have enthalpy and entropy relationships similar to those of alkanes for air/water partitioning and similar to those of polyfluorinated compounds for octanol/air partitioning, but more like those for benzoates and phenolic compounds for octanol/water partitioning. The temperature dependence of the partition coefficients of TMS is different from those of VMS and is more like that of alcohols, phenols, and sulfonamides. Environ Toxicol Chem 2014;33:2702–2710. © 2014 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals, Inc.
Assessing Quantitative Literacy in Higher Education: An Overview of Existing Research and Assessments With Recommendations for Next‐Generation Assessment
Authors: Roohr Katrina Crotts , Graf Edith Aurora , Liu Ou Lydia
Published: September 2014

Quantitative literacy has been recognized as an important skill in the higher education and workforce communities, focusing on problem solving, reasoning, and real‐world application. As a result, there is a need by various stakeholders in higher education and workforce communities to evaluate whether college students receive sufficient training on quantitative skills throughout their postsecondary education. To determine the key aspects of quantitative literacy, the first part of this report provides a comprehensive review of the existing frameworks and definitions by national and international organizations, higher education institutions, and other key stakeholders. It also examines existing assessments and discusses challenges in assessing quantitative literacy. The second part of this report proposes an approach for developing a next‐generation quantitative literacy assessment in higher education with an operational definition and key assessment considerations. This report has important implications for higher education institutions currently using or planning to develop or adopt assessments of quantitative literacy.
One‐Pot Regioselective Synthesis of Novel Oximino Ester‐Containing 1‐Aryl‐4‐chloro‐3‐oxypyrazoles as Potential Fungicides
Authors: Li Yi , Liu Yuan‐Yuan , Chen Nan‐Qing , Lü Kun‐Zhi , Xiong Xiao‐Hui , Li Jie
Published: September 2014

A novel, functional‐group‐tolerant, and highly regioselective one‐pot synthesis of six 4‐chloro‐1‐aryl‐3‐oxypyrazoles, 8a–8f, containing an oximino ester moiety has been developed. Their structures were characterized by 1H‐ and 13C‐NMR, IR, MS, and elemental analyses. The regioselectivity of the reaction was also determined by single‐crystal X‐ray diffraction analysis of product 8d. The reaction pathway, proposed with the aid of DFT calculations, likely proceeds via a DMF‐catalyzed mechanism, which involves an electrophilic attack by SOCl2 and two nucleophilic substitutions by benzyl bromide (BnBr) and Cl−, respectively, as the key steps. A preliminary in vitro bioassay indicated that most compounds exhibited good fungicidal activities against Sclerotinia sclerotiorum and Gibberella zeae. Especially, 8d and 8e displayed higher or similar fungicidal activities compared with pyraclostrobin at the concentration of 10 μg/ml.
Palmarumycins from the Endophytic Fungus Lasiodiplodia pseudotheobromae XSZ‐3
Authors: Lü Xiaojing , Chen Gang , Li Zhanlin , Zhang Yuhong , Wang Zaiying , Rong Weiwei , Pei Yuehu , Pan Huaqi , Hua Huiming , Bai Jiao
Published: September 2014

One new and three known spiro‐dioxynaphthalene compounds, related to palmarumycins, were isolated from the extracts of fungus Lasiodiplodia pseudotheobromae XSZ‐3. Their structures were established by spectroscopic methods (1D‐ and 2D‐NMR, HR‐ESI‐MS, etc.). The absolute configuration of 1 was determined by comparison of quantum‐chemical TDDFT (time‐dependent density‐functional theory) calculated and experimental ECD (electronic circular dichroism) spectra. The cytotoxic activities of 1–4 against HL‐60 cell line were evaluated by trypan blue‐staining assay.
Oligonucleotide Analogues with Integrated Bases and Backbone. Part 32
Authors: Schulze‐Adams Martina , Bernet Bruno , Touboul David , Egli Daniel , Herdeis Lorenz , Vasella Andrea
Published: September 2014

The G[s]G dinucleoside 6 and the G[s]G* dinucleoside 8 were prepared by alkylation of the guanosine thiols derived from 2 and 5, respectively, by the C(8)‐chloromethylated guanosine 4 that was obtained from alcohol 3. Dinucleosides 6 and 8 were deacylated to 7 and 9, and fully deprotected to 10 and 11, respectively. The G[n]G dinucleoside 16 was obtained by reductive amination of aldehyde 13 with an iminophosphorane derived from azide 14 and deprotection of the resulting dimer 15. In the solid state of 6, and in a solution of 6 and 8 in CDCl3, HN(1/I) and HN(1/II) are engaged in intramolecular H‐bonds to the CO of the isobutyryl protecting groups, and HN of the isobutyryl group of unit I forms an interresidue, intramolecular H‐bond to N(7/II), leading to a syn orientation of the nucleobase at unit I, to a tg orientation of the sulfanyl moiety, and to an orthogonal orientation of the nucleobases, preventing any base pairing. The silylated and isopropylidenated dinucleosides 7 and 9 are present in DMSO solution as solvated monoplexes. Broad 1H‐NMR signals of the nucleosides 7 and 16 in CHCl3 solution evidence equilibrating G‐quadruplexes. The quadruplex formation of 7 and 16 was established by 1H‐NMR spectroscopy (only of 16), vapour pressure osmometry, mass spectrometry, and CD spectroscopy. The C(6(I))‐hydroxymethylated analogue 9 in CDCl3 and the fully deprotected dinucleosides 10 and 11 in H2O form only weakly ππ stacked associates, but no G‐quadruplexes, as evidenced by CD spectroscopy.
Global HR Roles and Factors Influencing Their Development: Evidence From Emerging Indian IT Services Multinationals
Authors: Thite Mohan , Budhwar Pawan , Wilkinson Adrian
Published: September 2014

The rapid growth of emerging markets’ multinational companies (MNCs) is a recent phenomenon and, as such, their nature and structure of key management processes, functions, and roles need further examination. While an abundance of low‐cost labor is often the starting point of competitive advantage for many of the emerging markets’ MNCs, it is the optimum configuration of people, processes, and technology that defines how they leverage their intangible resources. Based on case studies of four Indian IT services MNCs, involving 51 in‐depth interviews of business and human resource (HR) leaders at the corporate and subsidiary levels, we identify five key HR roles—namely, strategic business partner, guardian of culture, builder of global workforce and capabilities, champion of processes, and facilitator of employee development. The analysis also highlights that the HR function in Indian IT service MNCs faces several challenges in consolidating the early gains of internationalization, such as lack of decentralized decision making, developing a global mind‐set, localization of the workforce, and developing a global leadership pipeline. Based on our exploratory findings, we propose a framework outlining the global HR roles pursued by emerging IT services MNCs, the factors influencing them, and the challenges facing their HR function for future research. © 2014 Wiley Periodicals, Inc.
MRT Letter: Guided filtering of image focus volume for 3D shape recovery of microscopic objects
Authors: Mahmood Muhammad Tariq
Published: September 2014

In this letter, a shape from focus (SFF) method is proposed that utilizes the guided image filtering to enhance the image focus volume efficiently. First, image focus volume is computed using a conventional focus measure. Then each layer of image focus volume is filtered using guided filtering. In this work, the all‐in‐focus image, which can be obtained from the initial focus volume, is used as guidance image. Finally, improved depth map is obtained from the filtered image focus volume by maximizing the focus measure along the optical axis. The proposed SFF method is efficient and provides better depth maps. The improved performance is highlighted by conducting several experiments using image sequences of simulated and real microscopic objects. The comparative analysis demonstrates the effectiveness of the proposed SFF method. Microsc. Res. Tech. 77:959–963, 2014. © 2014 Wiley Periodicals, Inc.
Evaluating the thermal effects of translocation in a large‐bodied pitviper
Authors: Holding Matthew L. , Owen Dustin A.S. , Taylor Emily N.
Published: September 2014

Acute stressors can be costly, often requiring alteration of normal physiological processes to mitigate their effects. Animal translocation may be a very stressful event and result in a reduced ability to maintain homeostasis. The impacts of translocation on the thermal ecology of ectothermic vertebrates, which may rely on preferred habitats for thermoregulation, are currently unknown. In this study, 22 adult male Northern Pacific rattlesnakes (Crotalus oreganus oreganus) were implanted with automated temperature loggers and radio‐tracked. Snakes were assigned to one of three treatments: translocation, handling control, and undisturbed control. Short‐distance translocation (SDT) and handling treatments were applied weekly for 6 weeks. Hourly body temperature (Tb) was recorded during the course of the study. Mean Tb was impacted in a time‐dependent fashion, where translocated snakes had lower mean Tb than handled controls during the first week of the study only, especially the first 24 hr after translocation. Separating the dataset into day and night revealed that this effect was localized to Tb variation during the day only. Variance in temperature was not impacted by translocation or handling. Snake body mass and time of year were the major factors influencing the thermal profiles of these rattlesnakes. Thermal ecology in male rattlesnakes is resilient to SDT, suggesting that they quickly resume normal behaviors following repeated bouts of acute capture stress and disturbance of their spatial ecology. This study provides support for SDT as a safe measure for mitigating human–snake interactions and facilitating conservation practices regarding male snakes, which are the most frequently encountered sex. J. Exp. Zool. 321A: 442–449, 2014. © 2014 Wiley Periodicals, Inc.
Sensory perceptions of individuals exposed to the static field of a 7T MRI: A controlled blinded study
Authors: Friebe Björn , Wollrab Astrid , Thormann Markus , Fischbach Katharina , Ricke Jens , Grueschow Marcus , Kropf Siegfried , Fischbach Frank , Speck Oliver
Published: September 2014

Purpose

To determine the subjective experience of subjects undergoing 7T magnetic resonance imaging (MRI) compared to a mock scanner with no magnetic field.

Methods and Materials

In all, 44 healthy subjects were exposed to both the B0 field of a 7T whole‐body MRI and a realistic mock scanner with no magnetic field. Subjects were blinded to the actual field strength and no scanning was performed. After exposure, subjects rated their experience of potential sensory perceptions.

Results

The most frequently observed side effect was vertigo while entering the gantry, which was reported by 38.6% (n = 17). Other frequent side effects were the appearance of phosphenes (18.2%, n = 8), thermal heat sensation (15.9%), unsteady gait after exposure (13.6%, n = 6), and dizziness (13.6%). All side effects were reported significantly more often after 7T exposure. Nine subjects (20.5%) did not report any sensory perceptions at all, ie, neither in the 7T scanner nor in the mock scanner.

Conclusion

Light, acute, and transient sensory perceptions can occur in subjects undergoing ultrahighfield MRI, of which vertigo seems to be the most frequently reported. Possible psychological effects might contribute to the emergence of such sensory perceptions, as some subjects also reported them to appear in a realistic mock scanner with no magnetic field. J. Magn. Reson. Imaging 2015;41:1675–1681. © 2014 Wiley Periodicals, Inc.
Interspecies comparison of subchondral bone properties important for cartilage repair
Authors: Chevrier Anik , Kouao Ahou S. M. , Picard Genevieve , Hurtig Mark B. , Buschmann Michael D.
Published: September 2014

Microfracture repair tissue in young adult humans and in rabbit trochlea is frequently of higher quality than in corresponding ovine or horse models or in the rabbit medial femoral condyle (MFC). This may be related to differences in subchondral properties since repair is initiated from the bone. We tested the hypothesis that subchondral bone from rabbit trochlea and the human MFC are structurally similar. Trochlea and MFC samples from rabbit, sheep, and horse were micro‐CT scanned and histoprocessed. Samples were also collected from normal and lesional areas of human MFC. The subchondral bone of the rabbit trochlea was the most similar to human MFC, where both had a relatively thin bone plate and a more porous and less dense character of subchondral bone. MFC from animals all displayed thicker bone plates, denser and less porous bone and thicker trabeculae, which may be more representative of older or osteoarthritic patients, while both sheep trochlear ridges and the horse lateral trochlea shared some structural features with human MFC. Since several cartilage repair procedures rely on subchondral bone for repair, subchondral properties should be accounted for when choosing animal models to study and test procedures that are intended for human cartilage repair. © 2014 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 33:63–70, 2015.
Influence of low‐molecular‐weight glutenin subunit genes at Glu‐A3 locus on wheat sodium dodecyl sulfate sedimentation volume and solvent retention capacity value
Authors: Li Zhixia , Si Hongqi , Xia Yunxiang , Ma Chuanxi
Published: September 2014

BACKGROUND

To understand the effect of low‐molecular‐weight (LMW) glutenin alleles at the Glu‐A3 locus on sodium dodecyl sulfate (SDS) sedimentation volume and solvent retention capacity (SRC) values, 244 accessions of Chinese wheat (Triticum aestivum L.) mini core collections were investigated. In this study the significant differences in wholemeal flour SDS sedimentation volume and SRC values associated with specific glutenin alleles at the Glu‐A3 locus were explained.

RESULTS

Seven glutenin alleles at the Glu‐A3 locus were confirmed by locus‐specific polymerase chain reaction (PCR). SDS sedimentation volume and lactic acid SRC value were significantly affected by alleles Glu‐A3b and Glu‐A3g. Based on total average values, 28 varieties carrying Glu‐A3b had significantly higher means of SDS sedimentation volume and lactic acid SRC value, whereas 19 varieties carrying Glu‐A3g had significantly lower means. Alleles Glu‐A3d and Glu‐A3f significantly increased only SDS sedimentation volume and sucrose SRC value respectively. Correlation analysis showed that SDS sedimentation volume was uncorrelated with lactic acid SRC and sucrose SRC values.

CONCLUSION

The Glu‐A3 LMW glutenin subunit could predict 12.8% of the variance in SDS sedimentation volume, 4.7% in lactic acid SRC and 6.4% in sucrose SRC. © 2014 Society of Chemical Industry
First Acyclic Diene Metathesis Polymerization Under Biphasic Conditions Using a Dicationic Ruthenium Alkylidene: Access to High‐Molecular‐Weight Polymers with Very Low Ruthenium Contamination
Authors: Zhao Jing , Wang Dongren , Autenrieth Benjamin , Buchmeiser Michael R.
Published: September 2014

The acyclic diene metathesis (ADMET) polymerization of 6‐hydroxy‐1,10‐undecadiene (M1) and 6‐acetoxy‐1,10‐undecadiene (M2) by the action of two different catalysts, i.e., the second‐generation Grubbs‐Hoveyda system ([RuCl2(IMesH2)(CH‐2‐(2‐PrO‐C6H4)]) (1) and the dicationic ruthenium alkylidene [Ru(DMF)3(IMesH2)(CH‐2‐(2‐PrO‐C6H4)] (2, IMesH2 = 1,3‐dimesitylimidazolin‐2‐ylidene) is reported. Biphasic conditions using 1‐butyl‐2,3‐dimethylimidazolium tetrafluoroborate ([BDMIM+BF4−]) and 1,2,4‐trichlorobenzene (TCB) are applied. Under the chosen conditions (T = 75 °C, 20 mbar), the use of catalyst 1 results only in the formation of low‐molecular‐weight polymers ( ≤ 10 000 g mol−1), while catalyst 2 allows for the high yield synthesis of high‐molecular‐weight polymers ( ≤ 40 000 g mol−1, yields ≤ 99%). Irrespective of the catalyst used, all polymers display a high trans‐content (>95%). Notably, Ru‐contamination of the target polymers without any additional purification is as low as 1.2 ppm with catalyst 2. Together with the high yields and high molecular weights, the low Ru‐contaminations clearly illustrate the advantages of the biphasic setup.

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Bayesian analysis of transverse signal decay with application to human brain
Authors: Bouhrara Mustapha , Reiter David A. , Spencer Richard G.
Published: September 2014

Purpose

Transverse relaxation analysis with several signal models has been used extensively to determine tissue and material properties. However, the derivation of corresponding parameter values is notoriously unreliable. We evaluate improvements in the quality of parameter estimation using Bayesian analysis and incorporating the Rician noise model, as appropriate for magnitude MR images.

Theory and Methods

Monoexponential, stretched exponential, and biexponential signal models were analyzed using nonlinear least squares (NLLS) and Bayesian approaches. Simulations and phantom and human brain data were analyzed using three different approaches to account for noise. Parameter estimation bias (reflecting accuracy) and dispersion (reflecting precision) were derived for a range of signal‐to‐noise ratios (SNR) and relaxation parameters.

Results

All methods performed well at high SNR. At lower SNR, the Bayesian approach yielded parameter estimates of considerably greater precision, as well as greater accuracy, than did NLLS. Incorporation of the Rician noise model greatly improved accuracy and, to a somewhat lesser extent, precision, in derived transverse relaxation parameters. Analyses of data obtained from solution phantoms and from brain were consistent with simulations.

Conclusion

Overall, estimation of parameters characterizing several different transverse relaxation models was markedly improved through use of Bayesian analysis and through incorporation of the Rician noise model. Magn Reson Med 74:785–802, 2015. © 2014 Wiley Periodicals, Inc.
ZTE imaging with enhanced flip angle using modulated excitation
Authors: Schieban Konrad , Weiger Markus , Hennel Franciszek , Boss Andreas , Pruessmann Klaas P.
Published: September 2014

Purpose

Zero echo time (ZTE) imaging is a fast, robust, and silent three‐dimensional technique for direct MRI of tissues with rapid transverse relaxation. It is conventionally performed with hard, block‐shaped excitation pulses short enough to excite spins uniformly over a large bandwidth. With this approach, the achievable flip angle (FA) is limited by the available B1 amplitude. The purpose of this work is to accomplish ZTE imaging with larger FAs by combined amplitude and frequency modulation of the excitation pulse while keeping the pulse duration short enough to limit acquisition dead time.

Methods

Quantitative performance criteria for FA yield and uniformity of radio frequency (RF) pulses were developed and used to optimize hyperbolic secant pulse shapes. The RF pulses were implemented on a 4.7 T animal MRI system, included in algebraic image reconstruction, and tested in experiments on phantoms and tissue samples.

Results

The optimized modulated pulses provide considerably improved performance with respect to uniformity and mean FA as compared with block‐shaped counterparts of the same maximum length. Using these pulses, ZTE images of excellent uniformity were obtained with enhanced FA and thus expanded contrast versatility.

Conclusion

The performance of ZTE imaging can be significantly improved by employing optimized short amplitude‐ and frequency‐modulated RF pulses. Magn Reson Med 74:684–693, 2015. © 2014 Wiley Periodicals, Inc.
A post‐mortem stereological study of striatal cell number in human obesity
Authors: Weise Christopher M. , Mouton Peter R. , Eschbacher Jennifer , Coons Stephen W. , Krakoff Jonathan
Published: September 2014

Objective

Neuroimaging studies have revealed abnormalities in brain structure, including the striatum, in obese people. In this study, the cellular and parenchymal basis for these findings in post‐mortem brain tissue was investigated.

Methods

Design‐based (unbiased) stereology combined with histochemical and immunocytochemical staining was used to quantify total number of neurons and astrocytes in post‐mortem striatal brain samples from nine obese (BMI 40.2 ± 6.1 kg/m2) and eight lean (BMI 24.4 ± 1.0 kg/m2) donors. Total numbers of Nissl‐stained neurons and glial fibrillary acidic protein‐immunopositive astrocytes were counted in 10 systematic‐random sections starting from the frontal pole of the striatum.

Results

There were no differences in mean total numbers of neurons (obese: 7.60 E+06; SD 2.50 E+06; lean: 7.85 E+06; SD 8.26 E+05; P < 0.78) or astrocytes (obese: 7.42 E+06; SD 2.27 E+06; lean: 7.43 E+06; SD 2.50 E+06; P < 0.99). A higher variance was found for number of neurons (P < 0.007) but not astrocytes (P < 0.72) in the obese group. Neuron/glia ratios were similar in both groups (obese: 1.07, SD 0.39; lean: 1.15, SD 0.37; P < 0.70) with an overall striatal neuron/glia ratio of 1.11 (SD 0.37) across the entire study population (n = 17).

Conclusions

No difference was found in the average numbers of neurons and astrocytes in the anterior striatum between lean and obese people. The morphological basis for structural brain changes in obesity requires further investigation.
Electron spin resonance investigations on graft copolymerization I. Poly(tetrafluoroethylene)–styrene system
Authors: Dobó J. , Hedvig P.
Published: September 2014

The decay of peroxy radicals was measured during the course of grafting styrene onto irradiated poly(tetrafluoroethylene) films. A linear decay was observed up to the time when the film was grafted through its whole thickness. The results of the electron spin resonance measurements could be correlated with the kinetic picture given earlier. In some cases, as a result of grafting, the appearance of fluorocarbon radicals was observed.
Systems for stereospecific polymerization of butadiene based on π‐crotyl and cyclopentadienyl complexes of transition metals
Authors: Tinyakova E. I. , Alferov A. V. , Golenko T. G. , Dolgoplosk B. A. , Oreshkin I. A. , Sharaev O. K. , Chernenko G. N. , Yakovlev V. A.
Published: September 2014

π‐Allyl systems based on bis‐π‐crotyl nickel in combination with halides of other metals were shown to be catalysts for the stereospecific polymerization of dienes. Correlation was made between the nature of the halogen in the active center (π‐allyl complex of nickel) and the microstructure of the polymer chain. The systems containing atoms of chlorine and iodine exhibit maximum stereospecificity and yield cis‐and trans‐polybutadiene, respectively. Bis‐π‐crotyl nickel provides the quantitative formation of the cyclic trimer of butadiene, predominantly trans,trans,trans‐isomer. Nickel hydrides in combination with transition metal halides and Lewis acids were shown to initiate the cis‐polymerization of butadiene. The process proceeds via the formation of π‐crotyl complexes of Ni and other metals. Systems based on biscyclopentadienylnickel and Lewis acids capable of producing stereoregular cis‐ and trans‐polybutadienes were investigated. Crotyl derivatives of chromium and titanium provide the formation of 1,2‐polybutadiene, while in combination with NiCl2 or TiI4, these crotyl derivatives are instrumental in producing 1,4‐cis‐polybutadiene. Addition of 1–2 oxygen atoms/molecule of triscrotyl chromium leads to formation of 1,4‐trans‐polybutadiene. Experimental evidence obtained indicates that the diene polymerization with chromium oxide catalyst involves the active centers of π‐allylic nature.
Synthesis and investigation of polyoxadiazoles
Authors: Korshak V. V. , Krongauz E. S. , Rusanov A. L.
Published: September 2014

By low temperature solution polycondensation in hexamethylphosphoramide of dicarboxylic acid dichlorides and dihydrazides of dicarboxylic acids or bisamidoximes, high molecular compounds with 1,3,4‐ and 1,2,4‐oxadiazole rings in the main chains have been prepared. Some features of the polycyclization reaction as well as the structure and properties of polymers obtained are discussed.
Investigation of branched polyarylates
Authors: Pavlova S. A. , Dubrovina L. V. , Timofeeva G. I.
Published: September 2014

In this paper is given an analysis of the results of the investigation of the polydispersity of polycondensation products, with linear polyarylates as an example. It has been shown that with an increase of the extent of reaction in the process of high‐temperature polycondensation, the role of the interchange reactions grows, leading to the permutation of the units of macromolecules. As a result of such permutation of the units the polydispersity of the samples obtained by the high‐temperature polycondensation decreases. For the products of the interphase polycondensation the coefficient of the polydispersity remains near two, regardless of the extent of reaction. The investigation of this work has shown that the MWD of the branched polyarylates resulting from the high‐temperature polycondensation is greatly influenced by the reaction of polycondensation equilibrium. In spite of the high degree of branching the polydispersity coefficient remains the same as for the linear polyarylates. It has been shown that the Zimm‐Stockmayer theory for the polyarylates in question gives more actual values of branching than the Zimm Kilb theory. The found empirical dependence between the parameters of the Mark‐Houwink equation for linear and branched polyarylates K = 0.268 (6.03 10−5)a is similar to that found earlier for the polyamides and polyesters.
The study of elementary stages in propylene polymerization catalyzed by VCl3–Al(i‐Bu)3
Authors: Novokshonova L. A. , Tsvetkova V. I. , Chirkov N. M.
Published: September 2014

The kinetics of propylene polymerization by a catalyst VCl3–Al(i‐Bu)3 and the molecular weight of polypropylene were studied within a pressure range of 60–500 mm. at 30–60°C. It was shown that within the range of sufficiently high monomer pressures the first reaction order with respect to the monomer is fulfilled, where chain limitation by the monomer is predominant. In the range of low monomer pressures, involving an increase of reaction order with respect to the monomer to the second for a limiting case, chain growth limitation by the alkyl metal and by spontaneous disproportionation play an important part. At 60°C. the constant of chain growth limitation by the monomer is almost 1.5 times higher than that for the alkyl metal and 40 times higher than that for spontaneous limitation. At least a part of the two latter reactions represents termination, after which the rate constant of addition to the active center for the first monomer molecule will be that of initiation which is lower than that of chain growth rate.
Investigation in the field of radiation‐induced solid‐state polymerization. XII. γ‐radiation‐initiated copolymerization of acrylic acid and acrylic amide in the solid, liquid, and supercooled liquid phase
Authors: Hardy Gyula , Nagy Lajos
Published: September 2014

The phase diagram of the acrylic amide–acrylic acid solid system is characterized by two eutectic compositions and by a molecular compound of 1:2 mole proportion with a maximum melting point. In the solid phase the rate of the copolymerization is the highest at the eutectic composition and passes through a minimum at the composition of the molecular compound. The composition of the copolymer formed in the solid phase reflects the structure of the solid phase and differs from the composition determined by the relative reactivity constants. In the supercooled liquid‐phase copolymerization proceeds at a higher rate than in the solid phase and probably according to an ionic mechanism.
Investigation of the radiation polymerization behaviors in the supercooled liquid and mesomorphous phase
Authors: Hardy Gy. , Fedorova N. , Kovács G. , Boros‐Gyevi J.
Published: September 2014

Polymerization of N‐vinylcaprolactam, dimethylitaconate, and vinylchloroacetate proceeds more rapidly in the supercooled liquid phase than in the solid phase. The effect is greater when supercooling is slow than when the process of supercooling is rapid. This phenomenon might be explained by the prearrangement of the monomer molecules without being fixed in the crystalline solid phase, such prearrangement being favorable from the viewpoint of polymerization. For monomers which polymerize near their melting point at a maximum rate, the presence of an even more ordered mesomorphous phase, similar to the liquid crystalline state, is assumed.
A study on orientation effects in polyethylene in the light of crystalline texture
Authors: Hay I. L. , Kawai T. , Keller A.
Published: September 2014

A comprehensive study of the molecular orientation and crystalline texture (the latter by low‐angle x‐ray diffraction supplemented by swelling measurements) in doubly oriented polyethylene on consecutive stages of heat annealing has allowed a picture of the structure and reorientation processes to be outlined. Thus even a drawn and rolled branched polyethylene is found to contain lamellae having {h0l}s basal planes with obliquities of 35–45°, in close analogy to those found in crystals grown from dilute solution and extracted from unoriented bulk linear polyethylenes. The initial ranges of the relaxation can be described by consecutive interlamellar and intralamellar slips activated by a rubber elastic compression. The cohesion between the lamellae opposing this is also found to be partially rubber elastic, and it is demonstrated that the resultant of the two elastic forces can be shifted by physical and chemical means. The individuality of the lamellae—requiring an appreciable amount of chain folding—is borne out. The possibility of producing macroscopic single‐crystal analogs is also demonstrated.
Anisotropy and structure in uniaxially stretched amorphous high polymers
Authors: Hennig Jürgen
Published: September 2014

When an amorphous polymer is stretched uniaxially, the chain molecules are oriented along the stretching direction. Orientation causes an anisotropy of the macroscopic physical properties with rotational symmetry about the stretching direction. The phenomenological treatment of the properties exhibited by a uniaxially oriented polymer follows mathematical methods known from crystal physics. Earlier data on anisotropy of linear thermal expansion, thermal conductivity, and linear compressibility for PVC are quantitatively explained with the aid of a known distribution function. The complete set of the five elastic compliances of hot‐stretched PVC are experimentally determined as function of stretch up to 180%. The correspondent compliances for the perfectly oriented material are calculated yielding, e.g., 5 × 1010 dynes/cm.2 for the Young's modulus along the chains. Finally, the lengths of the statistical segments in natural rubber and polychloroprene are evaluated from thermal conductivity measurements on these substances in the strained state. As is expected the polyisoprene chains prove to be considerably more flexible than those of polychloroprene.
ESR studies on transient free radicals during redox polymerization of some monomers
Authors: Fischer Hanns , Giacometti Giovanni
Published: September 2014

By application of a flow system, ESR spectra of transient free radicals are obtained during liquid‐phase polymerization initiated by ·CH3. The coupling constants of the radicals are discussed with respect to previous findings with \documentclass{article}\pagestyle{empty}\begin{document}$ \[{\rm HO}^ \bullet \] $\end{document}, \documentclass{article}\pagestyle{empty}\begin{document}$ \[{\rm NH}_2 \] $\end{document}, and ·CH2OH initiation. Some differences in the reactions of acrylic acid with HO· and ·CH3 are also reported. In total, the results strongly support the usual assumptions on reaction schemes of radical polymerization.
Graft copolymerization in aqueous dispersion of acrylic acid on olefin copolymer
Authors: Severini F. , Pegoraro M. , Tavazzani C. , Aurello G.
Published: September 2014

The polymerization of acrylic acid dissolved in an aqueous latex of an ethylene–propylene copolymer in the presence of benzoyl peroxide leads predominantly to the formation of graft copolymers. The amount of acrylic acid transformed into grafted chains is very high and can reach 80% of the starting monomer. Studies were made of the influence of reaction variables (temperature, initial concentration of acrylic acid and of benzoyl peroxide, concentration of the olefin copolymer in the latex used) upon the conversion rate of the monomer in a grafted polymer. Besides benzoyl peroxide, different initiators have been examined and compared. A fractionation method of the reaction crude is described, leading to the separation of the graft copolymer from the other products present. A reaction mechanism is proposed.
Rheological behavior of dilute polymer solutions in a general velocity field
Authors: Takserman‐Krozer R.
Published: September 2014

The rheological equation of state (constitutive equation) and the average rate of dissipation of energy flow are calculated for dilute solutions of flexible chain macromolecules. It is shown that such solutions may be considered as nonlinear viscoelastic fluids, the parameters of the equation of state being determined by the structural characteristics of the system: relaxation times τi and internal viscosity ρi. It is shown that in a general case the stress tensor is asymmetric; the antisymmetric part vanishes for systems with zero internal viscosity (ideally flexible chains). On the basis of structural data it is shown that the rheological equation of state may be linearized when the stress tensor is referred to the actual structure of the system. For the general case (ρi > 0, chains with limited flexibility) the average rate of dissipation of energy in the flowing system depends on the asymmetric part of the stress tensor as well as on the symmetric part.
Molecular structures of some low molecular weight model compounds with conformational features similar to those of high molecular weight compounds
Authors: Corradini P. , Ganis P. , Pedone C. , Sirigu A. , Temussi P. A.
Published: September 2014

An x‐ray study has been made of several alkylated dicarboxylic acids. The presence of atomic groupings similar to those in high molecular weight compounds has furnished interesting information about some structural features of high molecular weight compounds which cannot be directly established in the study of their structure. An interesting indication has been grasped about the non‐equivalence of the valence angles on CH2 and on CH(CH3. On this basis, the internal rotation angles, which characterize the conformation of isotactic and syndiotactic polypropylene and of the alternating crystalline copolymer ethylene–butene‐2‐cis, have been recalculated.
Study of aromatic sulfide polymers: Poly(2,5‐thienylene sulfide)
Authors: Jones K. , Moodie I. M.
Published: September 2014

Two methods of synthesis of poly(2,5‐thienylene sulfide) have been developed. The first of these is based on the uncatalyzed condensation of thiophene with sulfur chlorides and the second on the self‐condensation of 2‐chloro‐5‐thiophene thiol promoted by cuprous oxide in dimethylformamide. The polymers obtained by both methods are linear in structure and probably of low molecular weight. The polymer decomposes at 250–260°C. in air and under nitrogen. A study of molecular models suggests that steric hindrance may play an important part in the low thermal resistance of poly(2,5‐thienylene sulfide). Comparisons are drawn with the analogous poly(phenylene sulfide).
Charge interactions and association in polyelectrolyte solutions. I. Some general remarks
Authors: Mandel M.
Published: September 2014

Some aspects of charge interactions in polyelectrolyte systems as compared with ordinary electrolyte solutions are discussed. It is shown that two different kinds of association between counterions and polyions may be expected. These are distinguished as “physical” and “chemical” association, the difference being due to the exact nature of the interaction which is involved. The shortcomings of the usual theoretical treatments are emphasized, although no theoretical calculation is presented. Some experimental results are quoted to demonstrate the existence of different types of association. The necessity of not relying on one experimental method when investigating association phenomena in a given polyelectrolyte–counterion system is stressed.
Die Chemische Umsetzung des PVC mit Nucleophilen Reagentien
Authors: Wolkóber Zoltán , Varga Iraida
Published: September 2014

PVC in DMF gelöst, zeigt aromatischen Aminen, Aminoalkoholen bzw. aliphatischen Aminen gegenüber eine unterschiedliche Reaktionsbereitschaft, Substitutions‐ und Eliminierungsrenktionen erfolgen. Ein Aminüberschuss verschiebt die Reaktion in das SN‐Gebiet. Die geringste Reaktionsgeschwindigkeit wurde mit aromatischen Aminen festgestellt. Die Reaktionsgeschwindigkeit ist hoch bei Äthanolaminderivaten, am höchsten bei aliphatischen primären Aminen. Der Substitutionsgrad der Amine spielt eine bedeutend grössere Rolle als die pKa‐Werte. Unter den aliphatischen Aminen zeigen die quaternären Derivate die höchste Reaktionsgeschwindigkeit, innerhalb einiger Stunden gehen als in DMF zu 50% eine E′‐Reaktion mit dem PVC ein. Die Reaktionsbereitschaft der primären Amine liegt bedeutend niedriger, die der sekundären und tertiären sinkt weiter. Das Molekulargewicht des eingesetzten Alkohols beeinflusst bedeutend die Dehydrochlorierung des PVC durch Alkalialkoholate. Die höchste Dehydrochlorierungsgeschwindigkeit ergibt sich in Propylalkohol. Bei gleichem Molekulargewicht entscheidet die Konfiguration des Alkohols. Am langsamsten verläuft die Dehydrochlorierung bei Gegenwart von n‐Primäralkoholen.
Investigation of the hydrodynamic behavior of diene polymers and copolymers in ideal mixed solvents
Authors: Poddubnyi I. Ya. , Grechanovskii V. A. , Podalinskii A. V.
Published: September 2014

The hydrodynamic behavior of a number of diene polymers and copolymers (including cis‐1,4‐polybutadiene, cis‐1,4‐polyisoprene, butadiene–styrene, and butadiene–acrylonitrile copolymers) has been investigated in suitable mixed τ solvents. The relations of the basic hydrodynamic parameters, namely, the sedimentation constant, the diffusion coefficient, and the intrinsic viscosity, to molecular weight have been established, and may be used in calculating molecular weight distributions of the polymers investigated. For all polymer–solvent τ systems investigated the values of the parameter ϕ⅓P−1 are shown to be considerably lower than those predicted by theory. For all systems mentioned a distinct dependence of sedimentation and diffusion constants on concentration has been established. The experimentally observed regularities are interpreted on the assumption that the hydrodynamic interaction between macromolecules in sedimentation and diffusion processes affects the magnitude of the translational friction coefficient of the macromolecules. The effect of this dependence of sedimentation and diffusion constants on concentration is shown to decrease as the compactness of the macromolecular coils is increased, i.e., when the “specific dimensions” of the macromolecules \documentclass{article}\pagestyle{empty}\begin{document}$ \[\overline {r^2 } /M \] $\end{document}, in a given solvent are decreased.
The effect of the chain length on the optical activity of the helical polymers
Authors: Aslanyan V. M.
Published: September 2014

The theoretical interpretation data for optical activity of helical oligomers and for partly helixed polymeric chains require answers to the following questions: (1) How many monomeric units must each helical part contain so that its contribution to the optical rotation should be such as that of the same number of monomers in the infinite helix chain? (2) What role does the monomeric unit play at the ends of the helix section? (3) How far does the close interaction in the helix extend? The aim of this work is to answer these questions. The macromolecules crystallized in the helices were investigated. Cases were studied where only neighbor or neighbor and nearest nonneighbor monomeric units are interacted. It is shown that the contribution of the monomeric units in the helical section, consisting of twelve units to the optical rotation, practically coincides with that in the infinite helix.
The diffusion process in swelling ion exchanger beads
Authors: Dickel G. , Richter K.
Published: September 2014

Diffusion coefficients were evaluated from kinetic measurements on an ion exchanger by means of an equation of diffusion for swelling ion exchanger beads. It follows that the true diffusion coefficient changes with the ionic composition in such a way that it is smallest for the almost pure H form (DH) and greatest for the pure K form (DK). For the total change HR + K → KR + H of the pure H form to the K form the diffusion coefficient therefore must run from DH to DK. It is shown that one can describe the entire diffusion process with the constant DK value with the exception of a negligible induction period. On the other hand, one can describe the entire backward exchange process with the constant DH value. Therefore, the fact already found—that one can describe the exchange processes with constant but different diffusion coefficient for forward and backward reaction—is theoretically founded.
Méthode Graphique de Boltzmann pour la Détermination du Coéfficient de Diffusion de Translation
Authors: Soulie L.
Published: September 2014

Boltzmann has examined the solution of the equation with diffusion partial derivatives, the so‐called second Fick's equations when the translation diffusion coefficientDis a function of the concentration. In a particular initial concentration distribution he presents an integral solution of which one limit is infinite; the other limit containsx/√t, wherexis the distance from the initial separation surface andtthe time after the start of the diffusion. The concentration should therefore depend only on the variablex/√t. On the basis of theoretical considerations and experimental controls it is shown thatDis not a function only ofx/√t.
Étude des Complexes Polymères Dérivés du Tétracyanoéthylène
Authors: Rougée M. , André C.
Published: September 2014

Several polymer complexes of tetracyanoethylene (TCNE) and nickel acetyl acetonate have been prepared, taking special care for the purification and separation methods of the compounds which are obtained. The compounds are probably characterized by a conjugated double bonds system, as shown by infrared analysis and by the data of electric and magnetic measurements (RPE). The composition of the samples does not agree with a polyphthalocyanine type structure nor with that of a radical anion salt (TCNE−)2 · Ni+2, but corresponds to a TCNE/Ni ratio equal to 1. It is not yet possible to define the structure with accuracy, and other results will be necessary for this purpose. The properties of these compounds depend markedly on the condition of their preparation; the comparison with previous data is therefore delicate.