bluuebunny/crossref_metadata_2025 huggingface dataset:
Novel therapy for therapy‐resistant mantle cell lymphoma: Multipronged approach with targeting of hedgehog signaling
Authors: Hegde Ganapati V. , Nordgren Tara M. , Munger Corey M. , Mittal Amit K. , Bierman Philip J. , Weisenburger Dennis D. , Vose Julie M. , Sharp J. Graham , Joshi Shantaram S.
Published: April 2012

Mantle cell lymphoma (MCL) is one of the most aggressive B‐cell lymphomas with a median patient survival of only 5–7 years. The failure of existing therapies is mainly due to disease relapse when therapy‐resistant tumor cells remain after chemotherapy. Therefore, development and testing of novel therapeutic strategies to target these therapy‐resistant MCL are needed. Here, we developed an in vivo model of therapy‐resistant MCL by transplanting a patient‐derived MCL cell line (Granta 519) into NOD/SCID mice followed by treatment with combination chemotherapy. Cytomorphologic, immunophenotypic, in vitro and in vivo growth analyses of these therapy‐resistant MCL cells confirm their MCL origin and resistance to chemotherapy. Moreover, quantitative real‐time PCR revealed the upregulation of GLI transcription factors, which are mediators of the hedgehog signaling pathway, in these therapy‐resistant MCL cells. Therefore, we developed an effective therapeutic strategy for resistant MCL by treating the NOD/SCID mice bearing Granta 519 MCL with CHOP chemotherapy to reduce tumor burden combined with GLI‐antisense oligonucleotides or bortezomib, a proteosome inhibitor, to target therapy‐resistant MCL cells that remained after chemotherapy. This regimen was followed by treatment with MCL‐specific cytotoxic T lymphocytes to eliminate all detectable leftover minimal residual disease. Mice treated with this strategy showed a significantly increased survival and decreased tumor burden compared to the mice in all other groups. Such therapeutic strategies that combine chemotherapy with targeted therapy followed by tumor‐specific immunotherapy are effective and have excellent potential for clinical application to provide long‐term, disease‐free survival in MCL patients.
ATRP with Alkyl Pseudohalides Acting as Initiators and Chain Transfer Agents: When ATRP and RAFT Polymerization Become One
Authors: Nicolaÿ Renaud , Kwak Yungwan
Published: April 2012

All controlled radical polymerization (CRP) procedures rely on a dynamic and rapid equilibrium between dormant and active species. This equilibrium can be established through different mechanisms and all the resulting CRP processes have their own advantages and limitations. Therefore, it becomes interesting to investigate the possibility of combining CRP techniques to eliminate specific drawbacks of each individual procedure. Atom transfer radical polymerization (ATRP) with alkyl pseudohalides acting as initiators and chain transfer agents was developed for that purpose. The process relies on a dual mechanism involving both activationdeactivation and reversible additionfragmentation chain transfer (RAFT). This peculiar characteristic of ATRP with alkyl pseudohalides acting as chain transfer agents made it possible to overcome some of the limitations typically associated with conventional ATRP and RAFT polymerization as well as to prepare new responsive materials.
Assessment on pollution of ochratoxin a in grain in China and its apoptosis effect on vitro‐cultured human tubular kidney cells
Authors: Li Zengning , Zhang Xianghong , Cui Jinfeng , Kang Weijun
Published: April 2012

Ochratoxin A (OTA) is nephrotoxic, immunosuppressive, and teratogenic in many species and is a possible human carcinogen. In this study, we investigated the OTA pollution situations of grains in northern China and the signaling pathway that mediated OTA‐induced apoptosis in human tubular kidney cells (HKCs). Samples of grains collected from three representative areas were determined by using high‐performance liquid chromatography fluorescence method. The effects of OTA on cell apoptosis, caspase‐3, Bax, and Bcl‐2 expression, and phosphorylation of c‐Jun NH2 terminal kinase (JNK) were detected in cultured HKCs via flow cytometry (FCM), Hoechst 33258 staining, and Western blot. It showed that OTA pollution of edible grains was very common in north China. OTA could affect caspase‐3, Bax, and Bcl‐2 expression and increased cell apoptosis in cultured HKCs. The JNK signalling pathway might play an important role during these cellular events. © 2012 Wiley Periodicals, Inc. J Biochem Mol Toxicol 26:139–146, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/jbt.20420
Functional heterogeneity of mesenchymal stem cells: Implications for cell therapy
Authors: Phinney Donald G.
Published: April 2012

The term mesenchymal stem cell (MSCs) was adopted in the 1990s to describe a population of bone‐marrow‐derived cells that demonstrated the capacity for tri‐lineage differentiation at a clonal level. Research conducted during the ensuing decades has demonstrated that MSCs fulfill many functions in addition to connective tissue progenitors including contributing to the HSC niche and regulating the function of immune effector cells of both the innate and adaptive immune system. Despite these advances, fundamental aspects of MSC biology remain indeterminate. For example, the embryonic origin of MSCs and their niche in vivo remains a highly debated topic. More importantly, the mechanisms that regulate self‐renewal and lineage specification have also been largely unexplored. The later is significant in that MSC population's exhibit considerable donor‐to‐donor and intra‐population heterogeneity but knowledge regarding how different functional attributes of MSCs are specified at the population level is unknown. This poses significant obstacles in research and in efforts to develop clinical manufacturing protocols that reproducibly generate functionally equivalent MSC populations. Herein, I discuss data demonstrating that MSC populations are intrinsically heterogeneous, elaborate on the molecular basis for this heterogeneity, and discuss how heterogeneity impacts clinical manufacturing and the therapeutic potency of MSCs. J. Cell. Biochem. 113: 2806–2812, 2012. © 2012 Wiley Periodicals, Inc.
Influence of smoking cessation on carotid artery wall elasticity evaluated by echo‐tracking
Authors: Zhang Pu , Guo Ruijun , Xiao Dan , Chu Shuilian , Gong Lihuan , Zhang Chunmei , Jing Baihua , Li Mingqiu
Published: April 2012

Objective.

Exploring the use of echo‐tracking (ET) for evaluating changes in carotid artery wall elasticity after smoking cessation.

Methods.

Carotid artery ultrasound examination was performed in 67 male patients before and after smoking cessation treatment, for measurement of intimal media thickness (IMT), and ET measurement of wall elasticity variables, ie, wall stiffness index (β), pressure‐strain elastic modulus (Ep), compliance (AC), augmentation index (AI), and local pulse wave velocity (PWVβ). We also measured heart rate (HR), systolic pressure (Ps), diastolic pressure (Pd), total cholesterol (TC), triglyceride level (TG), low‐density lipoprotein (LDL), and high‐density lipoprotein (HDL).

Results.

Hyperlipemia and/or arterial hypertension and/or hyperglycemia were absent in 22 (group A1) and 12 (group B1) and present in 19 (group A2) and 14 (group B2) of the patients with successful (group A, n = 41) and unsuccessful (group B, n = 26) treatment, respectively. In the A1 group, there was no significant difference in AI before and after smoking cessation, whereas β, Ep, and PWVβ decreased, and AC increased (p< 0.05). None of these variables changed after smoking cessation in groups A2, B1, and B2. There was no change in IMT in either group. HR decreased and HDL increased in the A1 group, without change in Ps, Pd, TC, TG, and LDL. There was no change in HR, Ps, Pd, TC, TG, LDL, and HDL in groups A2, B1, and B2.

Conclusions.

ET can be used to evaluate quantitatively the impact of smoking cessation on common carotid artery wall elasticity. © 2012 Wiley Periodicals, Inc. J Clin Ultrasound, 2012
Identification of ages and determination of paeoniflorin in roots of Paeonia lactiflora Pall. From four producing areas based on growth rings
Authors: Zha Liang‐Ping , Cheng Ming‐En , Peng Hua‐Sheng
Published: April 2012

Growth rings were used to determine the root age of medicinal Paeonia lactiflora from four producing areas, and their corresponding paeoniflorin content were measured based on the identification of ages. Different P. lactiflora root samples of different ages were collected from the four major growing areas in China: Bozhou, Anhui Province; Pan'an, Zhejiang Province; Zhongjiang, Sichuan Province; and Heze, Shandong Province. The relationship between the number of growth rings and age was analyzed using hand sections and paraffin sections. The paeoniflorin content in the roots of different P. lactiflora cultivars from different growing areas was measured using high‐performance liquid chromatography (HPLC). The growth rings in the P. lactiflora roots were consistent with the age of the plant from Heze, Zhongjiang, Pan'an, whereas that for the P. lactiflora from Bozhou was one less than the age of the plant. The HPLC results show that the paeoniflorin content was highest in P. lactiflora ‘Baihuachuanshaoyao,’ followed by ‘Baihuahangshaoyao,’ ‘Honghuachuanshaoyao,’ and ‘Honghuahangshaoyao,’ ‘Bozhoushaoyao’ had the lowest levels of paeoniflorin. With increasing age, the paeoniflorin in the roots of the different P.lactiflora cultivars slowly declined or remained the same. In summary, the age of the roots of P. lactiflora from different growing areas can be determined using growth rings. The paeoniflorin content in the roots of P. lactiflora is correlated with cultivar and it was slowly declined with increasing age. Microsc. Res. Tech. 75:1191–1196, 2012. © 2012 Wiley Periodicals, Inc.
Comparing dry ashing and wet oxidation methods. The case of the rice husk (Oryza sativa L.)
Authors: Sun Xiuping , Wu Yan , Wang Changsui , Hill David V.
Published: April 2012

Experiments were conducted to determine the effects that different methods for the preparation of modern plant samples have on the resulting phytoliths using rice husks (Oryza sp.). The methods that are commonly used in phytolith extraction include (1) dry ashing, (2) acid extraction (3) a combination of both techniques. The results showed that processing methods have an impact on the morphology of two subspecies of rice phytoliths, dry ashing producing more conjoined cell phytoliths or multicells phytoliths than acid extraction. Using a combination of both methods resulted in the presence of fewer conjoined cells than dry ashing alone, but more conjoined cells than acid extraction. Alternative explanations are proposed to explain the formation of conjoined phytolith cells. Microsc. Res. Tech. 75:1272–1276, 2012. © 2012 Wiley Periodicals, Inc.
Walking, Paddling, Waddling: 3D Kinematics Anatidae Locomotion (Callonetta leucophrys)
Authors: PROVINI PAULINE , GOUPIL PIERRE , HUGEL VINCENT , ABOURACHID ANICK
Published: April 2012

Walking and paddling motions were studied in a semiaquatic bird, the ringed teal (Callonetta leucophrys), to investigate the motions associated with movements in two environments with radically divergent physical properties. A three‐dimensional (3D) kinematic reconstruction based on nonsynchronous biplanar cineradiographic data was used to quantify the 3D trajectories of the body and hind limb segments. Our study revealed that two subsystems interact to provide propulsion in water and on land. During paddling, the trunk, the femur, and the tibiotarsus are in a stable position and play the role of the hull. The femur and tibiotarsus are positioned laterally and parasagittaly and the intertarsal joint is fixed and positioned caudally allowing large amplitude movements of the “paddle” (tarsometatarsus and palmate foot). During walking, the center of mass is held above the medially oriented foot, providing stability during the single support phase. During stance, the foot is medially oriented because of the lateral and parasagittal positions of the tibiotarsus and tarsometatarsus during both walking and paddling. This position of the foot during walking imposes trunk translation and results in the typical waddling motion of Anatidae. This study provides new insights into how waddling motion relates to semiaquatic birds’ ability to move in both terrestrial and aquatic environments. J. Exp. Zool. 317:275–282, 2012. © 2012 Wiley Periodicals, Inc.
Perspectives on the Social Psychology of Creativity
Authors: Amabile Teresa M. , Pillemer Julianna
Published: April 2012

Scholars began serious study into the social psychology of creativity about 25 years after the field of creativity research had taken root. Over the past 35 years, examination of social and environmental influences on creativity has become increasingly vigorous, with broad implications for the psychology of human performance, and with applications to education, business, and beyond. In this article, we revisit the origins of the social psychology of creativity, trace its arc, and suggest directions for its future.
Domain Specificity and the Limits of Creativity Theory
Authors: Baer John
Published: April 2012

A growing body of research evidence suggests that creativity is very domain‐specific and that domain‐general skills or traits contribute little to creative performance. The term “creativity” is a convenient term for collecting many interesting artifacts, processes, and people into a single category, and the term “creative thinking skills” may be a useful way to connect a diverse set of unrelated cognitive processes that operate on different content and in different domains. These concepts are misleading, however, because although they connect things that may seem similar to observers, they lack any underlying cognitive psychological validity.

This has implications for the ways we understand and assess creativity, and also for how we should direct our efforts to develop creative‐thinking skills in diverse domains. Creativity training needs either to target the domains in which creativity enhancement is desired or to use a wide range of activities in diverse domains if the goal is more general improvement in many domains. Creativity assessment needs to focus on domain‐by‐domain assessment and to review findings based on allegedly domain‐general tests of creativity that may have misled researchers to unsupportable interpretations. Creativity theory needs to set more modest goals of domain‐by‐domain theory development and to recognize that theories that may seem domain‐general might better be understood as meta‐theoretical heuristics that do not actually describe domain‐general processes. These meta‐theories might in some cases help guide the search for domain‐based theories.
When Your Race Is Almost Run, but You Feel You're Not Yet Done: Application of the Propulsion Theory of Creative Contributions to Late‐career Challenges
Authors: Sternberg Robert J. , Kaufman James C.
Published: April 2012

The propulsion theory of creative contributions is a theory that focuses on how a creative act or product builds on and adds to knowledge in various fields. In this article, we apply the propulsion theory of creative contributions not to creative discoveries or inventions, but rather to late‐career decisions about future directions in which one can steer one's career. We consider eight different kinds of career decisions one can make—replication, redefinition, forward incrementation, advance forward incrementation, redirection, reconstruction/redirection, reinitiation, and synthesis. Each offers a viable option for closing out a creative career.
Quality characteristics of low‐fat chicken nuggets: effect of common salt replacement and added bottle gourd (Lagenaria siceraria L.)
Authors: Verma Arun Kumar , Sharma Brahma Deo , Banerjee Rituparna
Published: April 2012

BACKGROUND: There is growing demand for the meat products having healthier characteristics. In an endeavour to develop low‐salt, low‐fat and high‐fibre chicken nuggets an investigation was carried out to observe the effects of partial replacement (40%) of sodium chloride in pre‐standardised low‐fat chicken nuggets (Control, 20 g kg−1 NaCl) with a salt substitute blend as well as incorporation of bottle gourd (Lagenaria siceraria L.) in the resulting low‐salt, low‐fat products at three different levels, i.e. 50, 75 and 100 g kg−1 (Treatments, 12 g kg−1 NaCl) on the various quality attributes.

RESULTS: Sodium chloride replacement decreased (P < 0.01) emulsion and product pH, cooking yield, moisture, ash, yellowness, hue value and textural properties. pH values, moisture and dietary fibre increased (P < 0.01) while cooking yield, % protein, textural properties and total cholesterol were decreased with the incorporation of bottle gourd in low‐salt, low‐fat nuggets. Sensory attributes of the product were not affected with salt replacement; however, inclusion of bottle gourd at higher levels decreased (P < 0.05) flavour and texture scores.

CONCLUSION: The results suggest that low‐salt, low‐fat and high‐fibre chicken nuggets can be developed with the use of a salt substitute blend and bottle gourd without affecting their acceptability. Copyright © 2012 Society of Chemical Industry
Single treatment of non‐melanoma skin cancers using a pulsed‐dye laser with stacked pulses
Authors: Tran Hien T. , Lee Robert A. , Oganesyan Gagik , Jiang S. Brian
Published: April 2012

Background and Objective

Non‐melanoma skin cancers are the most common cause of cancer worldwide. Within this grouping, the most common skin cancer is basal cell carcinoma (BCC) followed by squamous cell carcinoma (SCC). Recent evidence has shown that BCCs can be cleared by a pulsed‐dye laser after multiple treatments using a single pass setting. Given the necessity for multiple treatments in the prior studies, we sought to determine whether tumor clearance could instead be achieved using a single treatment of the pulsed‐dye laser in a stacked pulse setting.

Study Design/Materials and Methods

Twenty patients with 23 biopsy‐proven BCCs and SCCIS that measured 0.4–3 cm in size and located on the trunk and extremities were recruited for this study. The lesions were randomized into three study arms: a control group (no treatment), first treatment group (S1), and second treatment group (S2). The S1 group was treated using a 595 nM pulsed‐dye laser (PDL) at pulse energy of 15 J/cm2, 3‐millisecond pulse length, with no dynamic cooling, using a 7‐mm spot size with 10% overlap of pulses and two passes. The S2 group was treated using the same 595 nM PDL at 7.5 J/cm2, 3‐millisecond pulse length, with no dynamic cooling, using a 10‐mm spot size with 10% overlap of pulses and double stacked pulses. All the treated lesions were treated with a 4 mm margin of clinically normal skin. The lesions were subsequently surgically excised and examined by histopathology.

Results

There was no significant difference in the dimensions of the tumors between the three study arms, with a mean area of 94 mm2 [SEM ± 15.2] for the control group, 88 mm2 [SEM ± 12.1] for the S1 treatment group, and 105 mm2 [SEM ± 23.6] for the S2 treatment group. In the control group, there were two out seven lesions with no residual tumors, representing a background tumor clearance rate of approximately 28%. The S1 treatment group had two out of eight lesions with no residual lesion representing a clearance rate of 25%, similar to the background clearance rate. The S2 treatment group had a clearance rate of five out seven lesions, representing a clearance rate of 71%. The two lesions with residual tumors were noted to be beyond the central treatment zone by histopathology and if excluded, results in a clearance rate of 100%. By the Fisher's exact test with a Bonferroni correction, there is a trend towards significance between the S2 treatment group and the control group with a P‐value of 0.028.

Conclusions

The results of our pilot study suggest that BCCs and SCCIS can be cleared in a single treatment using a pulsed‐laser in a stacked pulse setting. However, given the small sample size of this pilot study, further larger scale studies will be needed to determine statistical significance and long‐term recurrence rate and to further validate these findings. Lasers Surg. Med. 44: 459–467, 2012. © Wiley Periodicals, Inc.
Are the Interactions between Recombinant Prion Proteins and Polymeric Surfaces Related to the Hydrophilic/Hydrophobic Balance?
Authors: Vrlinic Tjasa , Debarnot Dominique , Legeay Gilbert , Coudreuse Arnaud , El Moualij Benaissa , Zorzi Willy , Perret‐Liaudet Armand , Quadrio Isabelle , Mozetic Miran , Poncin‐Epaillard Fabienne
Published: April 2012

New non‐fouling tubes are developed and their influence on the adhesion of neuroproteins is studied. Recombinant prion proteins are considered as a single component representative of hydrophobic proteins. Samples are stored for 24 h at 4 °C in tubes coated with two different coatings: poly(N‐isopropylacrylamide) as a hydrophilic surface and a plasma‐fluorinated coating as a hydrophobic one. The protein adhesion is monitored by ELISA tests, XPS and confocal microscopy. It appears that the highest recovery of recombinant prion protein in the liquid phase is obtained with the hydrophilic surface while the hydrophobic character of the storage tube induces an important amount of biological loss. However, the recovery is not complete even for tubes coated with poly(N‐isopropylacrylamide).

magnified image
Design of Serum Compatible Tetrary Complexes for Gene Delivery
Authors: Bahadur K. C. Remant , Thapa Bindu , Xu Peisheng
Published: April 2012

A novel gene delivery system, called PoSC, consisting of PEI, PSP, and HA is described. In contrast to the DNA/PEI/HA ternary system whose transfection efficiency decreases significantly with increasing serum concentration, PoSC exhibits a high transfection efficiency of about 51 and 87% for NIH3T3 and HCT116 cells, respectively, at 50% serum concentration. Furthermore, PoSC shows no cytotoxic effect at its working concentration. The overall results suggest that HA adsorption on cationic complexes enhances the transfection efficiency, while PSP is essential for high transfection efficiency at higher serum concentration.

magnified image
Fine Control of Polyester Properties via Epoxide ROP Using Monomers Carrying Diverse Functional Groups
Authors: You Zhengwei , Bi Xiaoping , Wang Yadong
Published: April 2012

Synthetic biodegradable polymers are important biomaterials. However, most of them are biologically inert. Free functional groups can allow easy biofunctionalization. Efficient introduction of functional groups to biodegradable polymers is still a challenge. Here, a practical strategy is presented to synthesize various functional polyesters with free hydroxyl groups polymerized via epoxide ring‐opening polymerization between dicarboxylic acids and diglycidyl dicarboxylates without protection and deprotection. The polymers exhibit a wide range of physical, thermal, and mechanical properties, and good cytocompatibilities. This synthetic platform is expected to lead to functional polymers useful for a wide variety of biomedical applications.

magnified image
Functionalization of Graphene Oxide by Two‐Step Alkylation
Authors: Huang Yi , Yan Weibo , Xu Yanfei , Huang Lu , Chen Yongsheng
Published: April 2012

A new reaction sequence for the chemical functionalization of graphene oxide (GO) consisting of the nucleophilic addition of n‐butyllithium (n‐BuLi) to the GO sheets and a subsequent coupling and etherification reaction of the intermediates (Bu‐GO)n−Lin+ and 2‐ethylhexyl bromide leading to functionalized GO is developed. The reaction is investigated. The results show that the n‐Bu and 2‐ethylhexyl are covalently attached to the GO sheets and many sp3 carbons are formed by addition reaction of n‐BuLi to the plane of GO. After functionalization, the dispersibility of functionalized GO in ortho‐dichlorobenzene (ODCB) increases significantly to 0.4 mg mL−1 and the structural integrity of the graphene sheets remained. Good electronic conductivity of the film prepared from functionlized GO (i‐Octyl‐Bu‐GO) in ODCB is obtained after high temperature annealing.
Hexahapto‐Metal Complexes of Single‐Walled Carbon Nanotubes
Authors: Kalinina Irina , Bekyarova Elena , Sarkar Santanu , Wang Feihu , Itkis Mikhail E. , Tian Xiaojuan , Niyogi Sandip , Jha Neetu , Haddon Robert C.
Published: April 2012

We report the preparation of organometallic side‐wall complexes of single‐walled carbon nanotubes (SWNTs) under conditions, which allow the study of both mono‐ and bis‐hexahapto SWNT coordination compounds [(η6‐SWNT)Cr(CO)3, (η6‐SWNT)Cr(η6‐C6H6), (η6‐SWNT)2Cr]. The results are interpreted in terms of exohedral and endohedral binding of chromium to the SWNT sidewalls and ligand competition reactions suggest that endohedral binding provides a very stable and kinetically inert mode of organometallic bonding. We demonstrate that the electrical conductivity of SWNT thin films are significantly enhanced by side‐wall bonding to Group 6 transition metals (M = Cr, Mo, and W), which serve to reduce the inter‐carbon nanotube junction electrical resistance by the formation of SWNT interconnects [(η6‐SWNT)2M].
Thermoresponsive Poly(2‐oxazoline) Molecular Brushes by Living Ionic Polymerization: Kinetic Investigations of Pendant Chain Grafting and Cloud Point Modulation by Backbone and Side Chain Length Variation
Authors: Zhang Ning , Luxenhofer Robert , Jordan Rainer
Published: April 2012

Molecular brushes of poly(2‐oxazoline)s were prepared by living anionic polymerization of 2‐iso‐propenyl‐2‐oxazoline to form the backbone and subsequent living cationic ring‐opening polymerization of 2‐n‐ or 2‐iso‐propyl‐2‐oxazoline for pendant chain grafting. In situ kinetic studies indicate that the initiation efficiency and polymerization rates are independent from the number of initiator functions per initiator molecule. This was attributed to the high efficiency of oxazolinium salt and the stretched conformation of the backbone, which is caused by the electrostatic repulsion of the oxazolinium moieties along the macroinitiator. The resulting molecular brushes showed thermoresponsive properties, that is, having a defined cloud point (CP). The dependence of the CP as a function of backbone and side chain length as well as concentration was studied.
Amino‐Acid‐Based Block Copolymers by RAFT Polymerization
Authors: Mori Hideharu , Endo Takeshi
Published: April 2012

This review summarizes recent advances in the design and synthesis of amino‐acid‐based block copolymers by reversible addition–fragmentation chain transfer (RAFT) polymerization of amino‐acid‐bearing monomers. We will mainly focus on stimuli‐responsive block copolymers, such as pH‐, thermo‐, and dual‐stimuli‐responsive block copolymers, and self‐assembled block copolymers, including amphiphilic and double‐hydrophilic block copolymers having tunable chiroptical properties. We will also highlight recent results in RAFT synthesis of amino‐acid‐based copolymers having various properties, such as catalytic and optoelectronic properties, cross‐linked block copolymer micelles, unimolecular micelles, and organic–inorganic hybrids.
Alkene Metathesis – A Tool for the Synthesis of Conjugated Polymers
Authors: Bunz Uwe H. F. , Mäker Dominic , Porz Michael
Published: April 2012

Alkene metathesis is a superb methodology. We report the progress using alkene metathesis in the synthesis of polymeric organic semiconductors. Three classes of polymers have been synthesized using acyclic diene metathesis (ADMET) or ring opening metathesis polymerization (ROMP), viz., poly(acetylene)s (PA), poly(arylene‐vinylene)s (PAV), and organometallic polymers. For PAs, ROMP of cyclooctatetraenes is best, whereas for PAV, both ADMET and indirect and direct ROMP are viable. Metathesis performs flawlessly with the correct monomers, as molybdenum and particularly the robust Ru carbenes demonstrate. When performing ROMP, one is often rewarded with structurally uniform polymers that can display very low polydispersities. Overall, metathesis is a powerful tool for the preparation of semiconducting polymers.
Synthesis of Polyolefins with Combined Single‐Site Catalysts
Authors: Mehdiabadi Saeid , Choi Yiyoung , Soares João B. P.
Published: April 2012

This manuscript shows how two single‐site catalysts can be used to produce polyolefins with complex microstructures that cannot be made using conventional Ziegler‐Natta or Phillips catalysts. In the first case study, thermoplastic polyolefins with heterogeneously branched structures are made by the copolymerization of ethylene, an α‐olefin, and an α‐ω diene using two metallocene catalysts in a two‐stage solution polymerization process. In the second, metallocenes and late transition metal catalysts are co‐supported on silica particles to produce ethylene/α‐olefin copolymers with inverse comonomer distribution in a single slurry reactor, by manipulating the comonomer reactivity ratios and chain walking frequencies of the catalyst pair.
Another Look at Site Heterogeneity in Ziegler‐Natta Catalysts for Polyolefin Production
Authors: McCoy John , Rawatlal Randhir
Published: April 2012

Ziegler Natta (ZN) catalysts are used to produce a wide range of polyolefins on an industrial scale. It has long been known that polymer produced on these catalysts have a relatively wide distribution in chain lengths; values for the Poly‐Dispersity Index (PDI) are generally well above 2, the value that would be expected if a single catalyst site type were active. These catalysts are conceptualised as containing a number of different active sites, which produce polymer with different average molecular weights. No physical explanation for the existence of different site types has been offered. In fact it has been shown that there is a close link between activity and oxidation state, and that only a single type of polymerising site is present. In this work, we propose that sites differ not in propagation rate but in the rate at which chain growth is terminated by a range of terminating agents, including hydrogen, monomer and co‐monomer. Each terminating agent is considered to act at a particular “pseudo‐site”. The ability of this interpretation to simulate a wide range of polymer properties is demonstrated. The pseudo‐sites model is then used to investigate experimentally‐determined chain length distribution data for ethylene‐1‐butene copolymer produced in lab reactors. It is shown that this new view of the heterogeneity of ZN active sites can successfully reproduce key polymer properties, including PDI and mean chain lengths. Based on these results, it is proposed that the pseudo‐sites model can be used to consolidate experimental data into a single set of parameters to describe the behaviour of a Ziegler‐Natta catalyst for polyolefin production.
Fractionation of Polypropylene Impact Copolymers Using Temperature Rising Elution Fractionation (TREF)
Authors: Mncwabe Sebenzile , Luruli Nyambeni , Marantos Evangelia , Nhlapo Piet , Botha Linda
Published: April 2012

Impact polypropylene copolymers (ICPs) have complex microstructures compared to homo‐ or random copolymers of propylene. Standard analytical techniques are unable to unpack the complex structure of impact copolymers, hence the need to fractionate the material. The investigation of poly(propylene‐ethylene) block copolymers was conducted in order to understand the copolymer composition and the role of particular components by fractionation. Temperature rising elution fractionation (TREF) was used for fractionation of ICPs which involves breaking up the polymer into small fractions that can be analysed further to give more understanding on the complex microstructures. Two ICP samples (ICP1 and ICP2) with different physical properties were fractionated. The bulk samples as well as the resulting fractions were further analysed using DSC, FTIR and DMA. Below 0 °C, the DMA results of the bulk sample with high ethylene content (ICP1) showed both low storage modulus and stiffness which is in line with expectations. However, it was interesting to note that above 0 °C the trend was reversed, thus ICP2 with low ethylene content had lower storage modulus and stiffness. The DSC and FTIR results of the fractions of the two samples revealed different or inhomogeneous distribution of ethylene content between the samples which explained differences in mechanical properties. The findings emphasize the contributions of phase separation and compatibility between the rubber and the matrix towards physical and mechanical properties.
Polymeric Micelles Using Pseudo‐Amphiphilic Block Copolymers
Authors: Benaglia Massimo , Spisni Enzo , Alberti Angelo , Giorgini Loris , Magnoni Francesco , Papi Alessio , Treossi Emanuele , Palermo Vincenzo
Published: April 2012

PS‐b‐PMA block copolymers carrying terminal anionic groups have been studied. Their synthesis is achieved by mean of 3‐(benzylsulfanyl thiocarbonylsulfanyl) propionic acid and 3‐(1‐phenylethylsulfanyl thiocarbonylsulfanyl) propanesulfonic acid sodium salt as RAFT agents. These block copolymers, when dispersed in methanol, display a pseudo‐amphiphilic behaviour and provide micelles that can be suspended in water by osmosis. During the self‐assembling process, the anionic terminations lead to the formation of nanosized monodispersed particles and confer stability to the micelles in aqueous media. The core of the micelles is loaded with Nile Red to achieve the intracellular delivery of a lipophilic substance; this has been demonstrated by Confocal Laser Scanning Microscopy. The particles, when loaded with Doxorubicin, are able to overcome the intrinsic resistance of LoVo‐MDR cancer cells. A further stabilization is given to the micelles by covalent shell crosslinking provided by triethylene glycol diacrylate. The increased intracellular stability of the crosslinked micelles makes them stain, when loaded with Nile Red, the aqueous cytosol instead of the lipophilic cellular compartments. The unimers constituting the micelles have been covalently labelled with fluorescein to follow their fate once incorporated into the cells.
Development of Polyelectrolyte Complex Microparticles for the Encapsulation of Isoniazid
Authors: Devi Nirmala , Kakati Dilip Kumar , Maji Tarun Kumar
Published: April 2012

Polyelectrolyte complex microparticles of different sizes were prepared by optimising the ratio of chitosan and sodium carboxy methyl cellulose (SCMC). The yield of the polyelectrolyte complex was dependent on the ratio of the two polymers and the pH of the medium. % yield and viscosity measurements were carried out to evaluate optimum pH and the ratio of the two polymers that produced the highest yield. Effect of various factors like amount of surfactant, concentration of polymer on the formation and size of the microparticles were investigated. The microparticles formed were pH‐responsive. These microparticles were used as carrier for isoniazid. The loading efficiency and release behaviour of loaded microparticles were found to be dependent on the amount of crosslinker used, concentration of drug and time of immersion. Maximum drug loading efficiency was observed at higher immersion time. The release rates of isoniazid at different pH were investigated and compared. The sizes of the microparticles were investigated by scanning electron microscopy. Microparticles were further characterised by FTIR and X‐ray diffraction study. The present work aims at producing microparticles as antitubercular drug carrier by using chitosan and SCMC as polymers, glutaraldehyde as crosslinker and sunflower oil as reaction medium.
Vinyl Monomers, Polymers and Supramolecular Assemblies from Aminocaprolactam
Authors: Tarkin‐Tas Eylem , Tas Huseyin , Mathias Lon J.
Published: April 2012

α‐Aminocaprolactam is a “green” monomer in two ways: it is a fermentation product from sugars, and its derivatives are naturally biocompatible and biodegradable. In this overview, the synthesis of a variety of α‐amino‐ε‐caprolactam (ACL) derivatives through reaction with acid chlorides, anhydrides, and alkyl halides is described first. The product vinyl and divinyl derivatives were then polymerized using free radical initiators, and the obtained polymers characterized by solution NMR spectroscopy, differential scanning calorimetry, and thermal gravimetric analysis. The homopolymers of these monomers displayed surprisingly high glass transition temperature (Tg) values plus unexpectedly large sub‐Tg transitions that are believed due to relaxation of hydrogen bonding of pendent ACL units that allows group rotation. Finally, bis‐ and tetra‐caprolactams of various diacid chlorides and diisocyantes were synthesized and shown to form self‐assembled polymers and networks with excellent physical and thermal properties.
Synthesis and Characterization of Allylmelamine Based Polymers
Authors: Gabriel Herbert , List Manuela , Schwarzinger Clemens
Published: April 2012

Novel linear polymers on the basis of allyl functionalized melamine derivatives, without using formaldehyde as cross‐linking agent, were created. Allylpentamethylmelamine and allyltetramethylmelamine were polymerized by free radical mechanism in substance. Allylpentamethyl‐melamine was also copolymerized with styrene by anionic polymerization. The new polymers offer a broad range of industrial application for melamine derivatives, not only in homopolymerization but also in the copolymerization with other monomers. For molar mass determination the polymer has been separated in different fractions by SEC and characterized by SEC and MALDI‐ToF mass spectrometry.
Adsorption of Methyl Orange, Pb2+ and Cd2+ from Aqueous Solution by Composites of Lignocellulose‐Montmorillonite Modified with Methacryloxypropyl Trimethoxysilane
Authors: Bunhu Tavengwa , Tichagwa Lilian
Published: April 2012

A composite material based on lignocellulose and montmorillonite clay (MPSgLig‐NaMMT) was prepared and evaluated as an adsorbent for the removal of pollutants (dyes and heavy metals) from aqueous solution. The lignocellulose‐montmorillonite composite was prepared by in situ intercalative polymerisation, using methacryloxypropyl trimethoxysilane (MPS) as a coupling agent. The composite material was characterised by FTIR, TGA and SAXS. The lignocellulose‐montmorillonite composite was assessed as an adsorbent for methyl orange dye from aqueous solution. The composite material showed enhanced adsorption of methyl orange (MetO) compared with the NaMMT or lignocellulose separately. Competitive adsorption studies were carried out from binary mixtures of MetO with Cd2+ or Pb2+ in aqueous solution. The adsorption process of MetO onto the composite material was found to follow the Freundlich adsorption model. The adsorption of methyl orange from binary mixtures, were found to follow both the pseudo first‐order and pseudo second‐order models.
The Combination of Liquid Chromatography and Mass Spectrometry Techniques for the Characterization of Aliphatic Polyesters
Authors: Pretorius Nadine O. , Simpson Jaylin M. , McLeary James B. , Pasch Harald
Published: April 2012

Aliphatic polyesters are industrially implemented in high performance coatings, paints and varnishes, however it is typically difficult to correlate the resulting properties with the synthesis parameters as these polymers vary in reactivity and application properties. Due to the stepwise polymerization mechanism, it is often assumed that copolyester synthesis by direct polyesterification will lead to randomized products. The formation of cyclic products by transesterification allows even further randomization, enabling a highly complex system. The different methods of polymer chromatography in combination with sophisticated spectroscopic techniques are useful tools for enabling the full description of the molecular heterogeneity of these complex polyesters. Through the use of SEC, HPLC, MALDI‐TOF and ESI‐MS information was obtained on the extent of heterogeneity found during the synthesis of model polyesters based on maleic anhydride and phthalic anhydride with propylene glycol which serve as building blocks for the more complex industrial variety.
Viscosity, Rheological and Morphological Properties of Sulfonated Poly(ether ether ketone): PEM Fuel Cell Membrane Material
Authors: Sultan Abdullah S. , Al‐Ahmed Amir , Zaidi S. M. Javaid
Published: April 2012

Viscosity and rheological properties of sulfonated poly(ether ether ketone) (SPEEK) have been investigated. Viscometric data were correlated by different models for polyelectrolytes. Results of viscosity for SPEEK show the characteristic properties of polyelectrolytes. Effects of parameters such as degree of sulfonation (DS), temperature, and type of solvents were investigated. Dynamic and steady shear measurements were carried out in an ARES rheometer at room temperature. It was observed that the degree of sulfonation (DS) and the solution concentration have an enormous effect on the rheological properties such as storage modulus, G′ and dynamic viscosity (η′). Membranes (thickness, ∼100 µm) were prepared by solution casting method using three different solvents, namely, N,N‐Dimethylacetamide, Dimethylsulfoxide and N,N‐Dimethylformamide. Scanning electron microscopy (SEM) and DSC studies were also carried out to study the morphological properties of these membranes. The degree of sulfonation (DS) of SPEEK, the solvent type and the temperature were found to have pronounced effects on the viscosity and rheological properties. SPEEK showed better properties in DMAc and results of SEM and DSC also confirm that membranes prepared in DMAc showed uniform morphology and higher thermal stability. These viscosity and rheological parameters give insight about the interaction of SPEEK with DMAc and these results can be helpful for membrane fabrication.
Electrochemical corrosion studies and pitting corrosion sensitivity of a self‐pierce rivet joint of carbon fibre reinforced polymer (CFRP) – laminate and EN AW‐6060‐T6
Authors: Mandel M. , Krüger L.
Published: April 2012

The galvanic corrosion of a self‐pierce rivet joint of EN AW‐6060‐T6 and a carbon fibre reinforced plastic (CFRP) laminate joint by an Almac®‐coated self‐pierce steel rivet was electrochemically investigated in a 5 wt.% sodium chloride solution. Furthermore, the joint was examined in a climate chamber according to the VDA 621‐415 (VDA = Verein Deutscher Automobilhersteller) standard test and microscopically observed. Electrochemical tests of the single components already reveal that a rivet joint of the materials can lead to pitting corrosion on the aluminium alloy surface and enforces the dissolution of the anti‐corrosion layer Almac® of the rivet. This predicted corrosion behaviour was confirmed by the microscopic observations after the exposure of the joint in the climate chamber.
Fabrication of carbon fibre reinforced, aluminium matrix composite by potassium iodide (KI) – potassium hexafluoro‐titanate (K2TiF6) flux
Authors: Juhasz K. L. , Baumli P. , Kaptay G.
Published: April 2012

Carbon fibres (CF) reinforced aluminium (Al) matrix composite material was fabricated using a special flux of potassium iodide (KI) with 10 weight% of potassium hexafluoro‐titanate (K2TiF6) at 820°C under protective argon atmosphere. The fabrication was performed with no extra pressure or mixing applied. Liquid Al spontaneously penetrated the space between the carbon fibres (or single fibres were spontaneously transferred from molten salt into liquid Al), due to the perfect wettability between these phases and the corresponding action of the interfacial capillary force. Perfect wettability is ensured by the formation of a thin metallic titanium carbide layer at the fibres/aluminium interface. Metallic titanium appears in liquid Al due to its exchange reaction with the K2TiF6 content of the molten salt.
Characterisation of the bonding zone of co‐extruded aluminium‐titanium‐compounds
Authors: Striewe B. , Grittner N. , von Hehl A. , Hunkel M. , Stelling O. , Schimanski K. , Schaper M. , Zoch H.‐W. , Bach F.‐W.
Published: April 2012

The combination of different metallic materials enables the design of lightweight structures with tailor‐made properties at global as well as local scale and offers great potential for advanced solutions especially for the aircraft and automobile sector. However, after conventional fusion joining, e. g. after laser beam welding, heat affected zones, porosity or grain growth may occur and impair the local properties. In contrast, by solid‐state joining techniques like co‐extrusion these disadvantages can be avoided. Therefore co‐extrusion exhibits an attractive solution for long products combining aluminium and titanium based alloys. Current investigations have been focused on the co‐extrusion of aluminium and titanium, where titanium is the reinforcing element that is inserted in aluminium profiles. In the context of a current research project the formation of the intermetallic layer and the mechanical properties were investigated in detail. In addition to that the influence on the intermetallic layer and the mechanical properties on heat treatment were investigated. The mechanical properties were determined by tensile tests. The intermetallic layers were analysed with light optical microscope, scanning electron microscope and electron probe micro analysis. During the co‐extruding an intermetallic layer with a thickness of 1 μm to 3 μm arises in the bonding zone between aluminium and titanium partner. Alloying elements from the aluminium alloy enrich in this layer. A subsequent heat treatment leads to an age hardening of the aluminium, however, it does not affect the layer thickness. The tensile tests specimen show different failure locations. The heat treatment leads to increased tensile strength values, but also to a decreased yield strength level.
Highly heat conductive open‐porous aluminium fibre based parts for advanced heat transfer applications
Authors: Andersen O. , Meinert J. , Studnitzky T. , Stephani G. , Kieback B.
Published: April 2012

Due to their oxygen affinity, aluminium alloys are difficult‐to‐sinter materials. Either mechanical destruction or the action of a liquid phase can be used to break oxide layers and thus achieve the desired diffusion bonds between the individual particles. In the present work, a liquid phase sintering approach is used in conjunction with high‐purity particulates and controlled processing conditions in order to obtain high‐purity, high‐porosity (up to 90 %) parts with an exclusively open porosity. Appropriate sinter conditions were determined with the help of thermodynamic calculations using the PANDAT software package. Bonding of the sintered fibre structures to tubes, sheets and other massive structures may be achieved by co‐sintering or brazing. The resulting metallic contacts allow for excellent heat transfer between the fibre structure and heat‐carrying fluids. These advantageous properties may be exploited in applications such as adsorption cooling devices or very fast phase‐change material (PCM) heat‐storage devices. The present study reports on the manufacturing of such PCM‐aluminium fibre compounds and their performance measured on a PCM storage demonstrator run in a laboratory environment.
Development of a mixer to fabricate particle stabilized aluminium matrix emulsions and monotectic alloys
Authors: Budai I.
Published: April 2012

Aluminum matrix monotectic alloys with a homogeneous distribution of the second phase droplets can be obtained in large ingots, if the droplets are stabilized by solid particles of optimized wettability at the interface of the two, immiscible liquid metals. In this paper, Al‐matrix emulsions with Cd‐rich droplets, stabilized by Al4Sr intermetallic particles are prepared, based on our previous paper. The new information in the present paper is the development of a new type of a mixer, allowing increased rotational speed, and hence, more efficient emulsification without the danger of mixing the liquid metals out of the crucible. As the comparative experiments proved, the ratio of emulsified Cd‐rich liquid was found to increase considerably when the old mixer was replaced by the new one. Particularly, there is no 1‐phase Cd‐rich sedimentation found at the bottom of the crucible when the mixer of the new design is applied.