bluuebunny/crossref_metadata_2025 huggingface dataset:
Randomized clinical trial comparing endovenous laser ablation with surgery for the treatment of primary great saphenous varicose veins
Authors: Darwood R J , Theivacumar N , Dellagrammaticas D , Mavor A I D , Gough M J
Published: February 2008

Background

Endovenous laser ablation (EVLA) is a minimally invasive technique for treating varicose veins due to truncal vein incompetence. This randomized trial compared EVLA with conventional surgery in patients with primary saphenofemoral and great saphenous vein (GSV) reflux.

Methods

Consecutive consenting patients with symptomatic varicose veins were randomized to EVLA 1 (stepwise laser withdrawal), EVLA 2 (continuous laser withdrawal) or surgery (saphenofemoral ligation, GSV stripping, multiple phlebectomies). Principal outcome measures were abolition of GSV reflux and improvement in Aberdeen Varicose Vein Symptom Score (AVVSS) 3 months after treatment.

Results

GSV reflux was abolished in 41 of 42 legs treated with EVLA 1, 26 of 29 following EVLA 2 and 28 of 32 after surgery (P = 0·227). The median (interquartile range, i.q.r.) AVVSS improvement was similar: 9·38 (4·54–14·93) with EVLA 1, 10·26 (5·03–15·03) after EVLA 2 and 8·36 (4·54–13·21) following surgery (P = 0·694). Return to normal activity (median (i.q.r.) 2 (0–7) versus 7 (2–26) days; P = 0·001) and work (4 (2–7) versus 17 (7·25–33·25) days; P = 0·005) was quicker after EVLA by either method.

Conclusion

Abolition of reflux and improvement in disease-specific quality of life was comparable following both EVLA and surgery. The earlier return to normal activity following EVLA may confer important socioeconomic advantages. Registration number: ISRCTN99270116 (http://www.controlled-trials.com).
Vaccination of asplenic or hyposplenic adults
Authors: Mourtzoukou E G , Pappas G , Peppas G , Falagas M E
Published: February 2008

Background

Sepsis is a feared complication in patients with an absent or dysfunctioning spleen.

Methods

A literature search was undertaken to identify recommendations for vaccination in asplenic or hyposplenic adults, and published data regarding the effectiveness of the vaccines in reducing the incidence of infections, and vaccine failures.

Results

Various committees and organizations recommend that the pneumococcal, meningococcal and Haemophilus influenza vaccine, plus booster doses, should be administered to patients with an absent or dysfunctional spleen. However, adherence to such recommendations varies. Furthermore, vaccine failures still occur in a subset of properly immunized individuals. Immunocompromised individuals, in particular, have a greater risk of inadequate antibody response.

Conclusion

Immunization is partially responsible for the observed reduction in sepsis after splenectomy.
Antiangiogenic therapy and surgical practice
Authors: John A R , Bramhall S R , Eggo M C
Published: February 2008

Background

Antiangiogenic therapy has become a reality with the recent introduction of bevacizumab, a monoclonal antibody against vascular endothelial growth factor.

Methods

Relevant medical literature from PubMed, National Institute for Health and Clinical Excellence and National Institutes of Health websites to August 2007 was reviewed.

Results and conclusions

Although often described as the fourth modality of treatment after surgery, radiotherapy and chemotherapy, many antiangiogenic drugs have failed to live up to expectations. Nevertheless, research continues and there are reasons to believe that antiangiogenic therapy may yet have a future in the clinical setting.
Local excision and endoscopic posterior mesorectal resection versus low anterior resection in T1 rectal cancer
Authors: Tarantino I , Hetzer F H , Warschkow R , Zünd M , Stein H J , Zerz A
Published: February 2008

Background

Rectum-preserving endoscopic posterior mesorectal resection (EPMR) removes the local lymph nodes in a minimally invasive manner and completes tumour staging after transanal local excision (TE). The aim of this study was to compare the morbidity and mortality of TE and EPMR with those of low anterior resection (LAR) in patients with T1 rectal cancer.

Methods

Between 1996 and 2006 EPMR was performed 6 weeks after TE in 18 consecutive patients with a T1 rectal cancer. Morbidity and mortality were recorded prospectively and compared with those in a group of 17 patients treated by LAR. Lymph node involvement and local recurrence rate were analysed in both groups.

Results

Two major and three minor complications were noted after EPMR, and four major and four minor complications after LAR (P = 0·402 for major and P = 0·691 for minor complications). Median number of lymph nodes removed was 7 (range 1–22) for EPMR and 11 (range 2–36) for LAR (P = 0·132). Two of 25 patients with a low-risk rectal cancer were node positive. No patient developed locoregional recurrence.

Conclusion

EPMR after TE is a safe option for T1 rectal cancer. This two-stage procedure has a lower morbidity than LAR and may reduce locoregional recurrence compared with TE alone.
Peritoneal adhesions
Authors: Harris D A , Topley N
Published: February 2008

An unsolved problem
Effectiveness of an hypnotic imagery intervention on reducing alexithymia
Authors: Gay Marie‐Claire , Hanin Dorothée , Luminet Olivier
Published: February 2008

The therapeutic potential of the use of mental representations, such as mental images, might be an interesting approach in the treatment of people who are severely impaired with respect to the processing of emotion, and in particular the activation of mental images. That is the case of alexithymia, which is a multifaceted construct comprising (a) difficulty identifying feelings and distinguishing between feelings and the bodily sensations of emotional arousal; (b) difficulty describing feelings to others; (c) a restricted imagination, as evidenced by a paucity of fantasies; and (d) a cognitive style that is literal, utilitarian, and externally oriented (Taylor and Bagby, 2000). Thirty‐one alexithymic female students were randomly distributed into two conditions: hypnotic imagery condition and control condition. Participants in the hypnotic imagery condition took part in an 8‐session individual training programme. The findings indicate that hypnosis is an effective technique for obtaining a decrease in alexithymic scores. The findings also indicate that changes in mood states are not involved in the change in alexithymia scores. This suggests that hypnosis has exerted a direct effect upon alexithymia (not attributable to anxiety or depression), and consequently demonstrates that it is possible to exert an effect (i) upon alexithymia without targeting a decrease in anxiety or depression scores, (ii) upon alexithymic people with no anxiety or depression problems, as anxiety and depression are not the therapeutic determinant of the therapeutic response. Copyright © 2008 British Society of Experimental & Clinical Hypnosis. Published by John Wiley & Sons, Ltd.
The therapist as a travelling companion to the chronically ill: hypnosis and cancer related symptoms
Authors: Ebell Hansjörg
Published: February 2008

The complex interaction of pain, other symptoms and suffering in cancer patients requires a treatment approach that integrates psychological as well as pharmacological interventions. The supplementation of a pharmacological pain treatment concept based on WHO‐guidelines by the use of self hypnosis was examined in a controlled clinical follow up study: 61 of 342 patients with cancer related pain referred to the Interdisciplinary Pain Unit of Munich University Clinic were included. In a cross‐over design they were randomly assigned to two different successions of treatments after a 2‐week period of establishing optimal medication: either AB (A: using self‐ hypnosis and analgesics, followed by B: pharmacological treatment alone, 4 weeks each) or BA (B: continuing pharmacological treatment alone and then A: using additional self‐hypnosis). Patients themselves evaluated therapeutic effectiveness with the help of visual analogue scales (VAS) in a ‘pain diary’ for a total of 10 weeks. On account of a carryover‐effect caused by the beneficial effects of self‐hypnosis the ‘cross‐over’ did not show statistical significance. Using a parallel design we found a statistically significant reduction of pain and suffering after the first four weeks for treatment A (with self‐hypnosis) in comparison to treatment B (without self‐hypnosis). The utilization of hypnosis requires an intensive subjective exchange over a period of time between the patient and the therapist, who embark as travelling companions on a journey through uncharted territory. Three case reports serve as an example for three different ‘time windows’ of this travelling companionship of therapists and patients: short term/crisis intervention, cooperation for several weeks/coping enhancement, and long term/psychotherapy. Copyright © 2008 British Society of Experimental & Clinical Hypnosis. Published by John Wiley & Sons, Ltd.
Thromboembolic events with lenalidomide‐based therapy for multiple myeloma
Authors: Menon Smitha Patiyil , Rajkumar S. Vincent , Lacy Martha , Falco Patrizia , Palumbo Antonio
Published: February 2008

BACKGROUND.

The purpose was to evaluate the incidence and risk factors of thromboembolism associated with lenalidomide therapy in newly diagnosed myeloma.

METHODS.

A pooled analysis was performed of patients with previously untreated multiple myeloma enrolled in clinical trials of lenalidomide‐based therapy at the Mayo Clinic, Rochester, Minnesota, and the Italian Myeloma Network, Italy. The incidence of thrombosis, the effect of risk factors such as steroid dose and erythropoietin supplementation, and the effect of prophylaxis were examined.

RESULTS.

In all, 125 patients enrolled in 3 clinical trials were identified. Patients were stratified based on the concomitant corticosteroid dose. Fifty‐two patients were in the high‐dose group (dexamethasone 40 mg, 12 days a month); 73 patients were in the low‐dose group (prednisone at any dose; or dexamethasone 40 mg, 4 days a month). A total of 110 patients were initiated on thromboprophylaxis; of these, 104 patients (95%) received aspirin. Ten patients (8%) developed deep vein thrombosis, including 4 who were not receiving any thromboprophylaxis at the time of the event. The rate of thromboembolic events was not different between patients who received concomitant erythropoietin therapy and those who did not, 4.8% and 8.6%, respectively (P = .54). A higher number of venous thrombotic episodes occurred in the high‐dose corticosteroid group compared with the low‐dose corticosteroid therapy group (12% vs 6%), but the difference was not statistically significant (P = .3).

CONCLUSIONS.

The incidence of deep vein thrombosis is lower than previously reported in the literature. There was a trend to a higher incidence of thrombosis in patients receiving high‐dose corticosteroid therapy. Cancer 2008. © 2008 American Cancer Society.
Schubprüfungen an geschosshohen Wänden – Grundlagen und Durchführung
Authors: Schermer Detleff , Fehling Ekkehard , Stürz Jochen
Published: February 2008

Die experimentelle Überprüfung der Schubtragfähigkeit geschosshoher Wände dient dem Ziel, neben der Bestimmung der Tragfähigkeit an sich auch das Trag‐ und Verformungsverhalten unter kombinierter N‐M‐V‐(Normalkraft‐Momenten‐Horizontalkraft)‐Beanspruchung zu untersuchen. Im Gegensatz zu herkömmlichen Versuchen nach dem vereinheitlichten Schubprüfverfahren des DIBt wird nicht eine Schubfestigkeit bestimmt, sondern das Ergebnis stellt die Schubtragfähigkeit des Bauteils insgesamt dar. Dieser Wechsel entspricht auch der Weiterentwicklung in der Normung, bei der die rechnerischen Nachweise als Vergleich von Tragfähigkeiten erfolgen.

Entscheidend für die Güte der Versuchsergebnisse sind die Randbedingungen in Form der Konstruktion der Versuchsstände, der Ausbildung der Lasteinleitungsdetails und der Versuchsdauern. Es werden nachfolgend Angaben zu der Lastgeschichte für statisch‐monotone und statisch‐zyklische Versuchsdurchführungen gegeben.

Mit Hilfe der beschriebenen Schubprüfungen kann das Verhalten von Mauerwerkswänden unter kombinierter Beanspruchung realitätsnah experimentell untersucht werden und künftig Basis von individuellen Bemessungs‐ und Anwendungsregeln sein.
Statistische Untersuchung der Druckfestigkeit von Porenbeton – Größeneffekt und Umrechnungsfaktoren
Authors: Wolf Susann , Walther Hartmut , Langer Peter , Stoyan Dietrich
Published: February 2008

Im Rahmen eines BMBF‐Projekts wurden von der Firma Xella Technologie‐ und Forschungsgesellschaft mbH und dem Institut für Stochastik der TU Bergakademie Freiberg Versuche zur Druckfestigkeit von Porenbeton durchgeführt und diese dann statistisch ausgewertet. Im Mittelpunkt stand der Größeneffekt, d.h. die Abhängigkeit der Druckfestigkeit von der Probengröße. Ein Größeneffekt wurde nur für Prüfkörper mit einer Kantenlänge von kleiner als 200 mm nachgewiesen, wobei mit abnehmender Prüfkörpergröße auch die Festigkeit sinkt. Das führt zu einem Faktor von 1,05 für die Umrechnung von Festigkeiten von Würfeln mit einer Kantenlänge von 100 mm auf handelsübliche Steine.
PI3 kinase/Akt activation mediates estrogen and IGF‐1 nigral DA neuronal neuroprotection against a unilateral rat model of Parkinson's disease
Authors: Quesada Arnulfo , Lee Becky Y. , Micevych Paul E.
Published: February 2008

Recently, using the medial forebrain bundle (MFB) 6‐hydroxydopmaine (6‐OHDA) lesion rat model of Parkinson's disease (PD), we have demonstrated that blockade of central IGF‐1 receptors (IGF‐1R) attenuated estrogen neuroprotection of substantia nigra pars compacta (SNpc) DA neurons, but exacerbated 6‐OHDA lesions in IGF‐1 only treated rats (Quesada and Micevych [2004]: J Neurosci Res 75:107–116). This suggested that the IGF‐1 system is a central mechanism through which estrogen acts to protect the nigrostriatal DA system. Moreover, these results also suggest that IGF‐1R‐induced intracellular signaling pathways are involved in the estrogen mechanism that promotes neuronal survival.In vitro, two convergent intracellular signaling pathways used by estrogen and IGF‐1, the mitogen‐activated protein kinase (MAPK/ERK), and phosphatidyl‐inositol‐3‐kinase/Akt (PI3K/Akt), have been demonstrated to be neuroprotective. Continuous central infusions of MAPK/ERK and PI3K/Akt inhibitors were used to test the hypothesis that one or both of these signal transduction pathways mediates estrogen and/or IGF‐1 neuroprotection of SNpc DA neurons after a unilateral administration of 6‐OHDA into the MFB of rats. Motor behavior tests and tyrosine hydroxylase immunoreactivity revealed that the inhibitor of the PI3K/Akt pathway (LY294002) blocked the survival effects of both estrogen and IGF‐1, while an inhibitor of the MAPK/ERK signaling (PD98059) was ineffective. Western blot analyses showed that estrogen and IGF‐1 treatments increased PI3K/Akt activation in the SN; however, MAPK/ERK activation was decreased in the SN. Indeed, continuous infusions of inhibitors blocked phosphorylation of PI3K/Akt and MAPK/ERK. These findings indicate that estrogen and IGF‐1‐mediated SNpc DA neuronal protection is dependent on PI3K/Akt signaling, but not on the MAPK/ERK pathway. © 2008 Wiley Periodicals, Inc. Develop Neurobiol 2008
Recoverable Phase‐Transfer Catalysts with Fluorinated Anions: Generation and Reactions of Dichlorocarbene and CCl3 Anion in the Heterogeneous System KOH(s)/CHCl3/nBu4NPF6
Authors: Kryshtal Galina V. , Zhdankina Galina M. , Zlotin Sergei G.
Published: February 2008

Tetraalkylammonium salts bearing PF6– and BF4– anions have been recognized as recoverable phase‐transfer catalysts for the synthesis of 1,1‐dichlorocyclopropane and α‐(trichloromethyl)carbinol derivatives from alkenes or aldehydes in the heterogeneous system KOH(s)/CHCl3. The catalysts retained their catalytic activity over several reactioncycles.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)
The integrated water balance and water temperature model LARSIM‐WT
Authors: Haag I. , Luce A.
Published: February 2008

The goal of this article is to describe the integrated water balance and water temperature model LARSIM‐WT (large area runoff simulation model‐water‐temperature). The integrated model is an extension of the water balance model LARSIM, which simulates all major aspects of the terrestrial water cycle. The newly added water temperature module allows simulation and forecasting of river water temperatures (RWTs) throughout the complete river network using a deterministic approach, accounting for heat exchange processes along the flow path as well as local sources such as thermal discharges. In addition, it is also possible to calculate RWTs with regression models for specific locations in the river network. Applying LARSIM‐WT to the 14 000 km2 watershed of the Neckar River showed that the model is well‐suited to simulate RWTs along with discharges. Forecast tests proved the adequacy of the model for operational RWT forecasting for up to seven days ahead. The model has been continuously used for automated daily river temperature and discharge forecasting for the Neckar River since 2004. Moreover, it has also been successfully applied to predict the impact of climate change on water temperatures in the Neckar River. Copyright © 2008 John Wiley & Sons, Ltd.
Hen egg white lysozyme fibrillation: a deep‐UV resonance Raman spectroscopic study
Authors: Xu Ming , Ermolenkov Vladimir V. , Uversky Vladimir N. , Lednev Igor K.
Published: February 2008

Amyloid fibrils are associated with numerous degenerative diseases. The molecular mechanism of the structural transformation of native protein to the highly ordered cross‐β structure, the key feature of amyloid fibrils, is under active investigation. Conventional biophysical methods have limited application in addressing the problem because of the heterogeneous nature of the system. In this study, we demonstrated that deep‐UV resonance Raman (DUVRR) spectroscopy in combination with circular dichroism (CD) and intrinsic tryptophan fluorescence allowed for quantitative characterization of protein structural evolution at all stages of hen egg white lysozyme fibrillation in vitro. DUVRR spectroscopy was found to be complimentary to the far‐UV CD because it is (i) more sensitive to β ‐sheet than to α ‐helix, and (ii) capable of characterizing quantitatively inhomogeneous and highly light‐scattering samples. In addition, phenylalanine, a natural DUVRR spectroscopic biomarker of protein structural rearrangements, exhibited substantial changes in the Raman cross section of the 1000‐cm–1 band at various stages of fibrillation. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The source of lamellar mitochondria‐rich cells in the air‐breathing fish, Trichogaster leeri
Authors: Lee Wen , Huang Chun‐Yen , Lin Hui‐Chen
Published: February 2008

Pavement cells and the mitochondria‐rich cells (MRCs) are two of the main types of cells in fish gill epithelia. The pavement cells are generally responsible for gas exchange and MRCs for ion regulation. MRCs are found especially in the trailing edge and the interlamellar region of gill filament. In some species, MRCs are also observed in the gill lamellae. A previous study reported the likelihood of having lamellar MRCs in air‐breathing fishes. Nevertheless, the source of lamellar MRCs is unclear. We used the air‐breathing fish, Trichogaster leeri, to investigate the source of proliferated cells on the lamellae when 5‐bromo‐2‐deoxyuridine (BrdU) was injected at different times before fish were sampled from deionized water. There were two major findings in this study. First, undifferentiated cells were found in the lamellae, as well as in the filaments. And, within 12–24 hr, a proliferated cell, identified as BrdU cell, could differentiate to an MRC in the gill lamellae. Second, the filaments and the lamellae in T. leeri responded to ionic stress differently but the proportion of the proliferated MRCs to the BrdU cells remained constant. Our results suggested that the lamellar MRCs were mainly differentiated from the cells that proliferated earlier from the lamellae. J. Exp. Zool. 309A:198–205, 2008. © 2008 Wiley‐Liss, Inc.
Separation and determination of biogenic amines in fish using MEKC with novel multiphoton excitation fluorescence detection
Authors: Feng Xiaojun , Chen Sheng , Xu Youzhi , Du Wei , Luo Qingming , Liu Bi‐Feng
Published: February 2008

Biogenic amines are a group of biological molecules derived from the enzymatic decarboxylation of natural amino acids. They can be found in a variety of foods and some of them are involved in essential cellular pathways regulating cellular functions. To address the issues raised by conventional detection methods for biogenic amines, such as laborious sample preparation and limited sensitivity, a new micellar electrokinetic chromatography scheme was developed based on multiphoton excitation fluorescence (MPEF) detection. Six FITC‐labeled biogenic amine species were used for the evaluation of this MEKC–MPEF method in comparison to single photon excitation fluorescence detection. The results indicated that MEKC–MPEF had superior resolution with a detection volume as low as aL. Quantitative analysis of varying concentrations of biogenic amine species has also been achieved suggesting a ymole mass detection limit, a linear dynamic range of about two orders of magnitude, and 95–105% recoveries. Furthermore, the biogenic amine profile of decayed oriental crucian carps was successfully determined and quantified using this new method.
Analytical results for 2‐D non‐rectilinear waveguides based on a Green's function
Authors: Ciraolo Giulio , Magnanini Rolando
Published: February 2008

We consider the problem of wave propagation for a 2‐D rectilinear optical waveguide which presents some perturbation. We construct a mathematical framework to study such a problem and prove the existence of a solution for the case of small imperfections. Our results are based on the knowledge of a Green's function for the rectilinear case. Copyright © 2008 John Wiley & Sons, Ltd.
Expression of FGF2 and TGFα and testis morphology during testicular hypertrophy subsequent to hemicastration in the neonatal boar
Authors: Wells R. , Scott P.T. , Harrison D.K. , Wreford N.G. , Duckett R. , Johnston S.D. , D'Occhio M.J.
Published: February 2008

The objective was to ascertain fibroblast growth factor‐2 (FGF2), epidermal growth factor (EGF), and transforming growth factor‐α (TGFα) mRNA expression and testis morphology during accelerated testicular growth after hemicastration in the neonatal boar. On Day 10 after birth (Day 0), boars were assigned to control (n = 28), no treatment; hemicastrated (n = 28), left testis removed. The right testis in both groups (n = 7) was removed on Days 5, 10, 15, and 20. Expression of mRNA for FGF2, EGF, and TGFα was determined by qRT‐PCR using TaqMan®. Testicular morphology was determined on Day 15. On Day 10, hemicastrated boars had a greater (P = 0.01) testis weight (6.2 ± 0.8 g; mean ± SEM) than controls (4.3 ± 0.4 g) and on Day 15 testis weight in hemicastrated boars (8.8 ± 0.8 g) was twice (P < 0.01) that of control boars (4.2 ± 0.3 g). Seminiferous tubule volume was approximately doubled in hemicastrated boars (P < 0.01) and was associated with an increase (P < 0.01) in Sertoli cell number. Interstitial compartment volume was greater (P < 0.01) in hemicastrated boars. Leydig cell numbers were similar (P = 0.14) but volume was greater (P < 0.01) for hemicastrates. There were no differences (P > 0.05) between control and hemicastrated boars in TGFα or FGF2 expression on Day 5 or Day 10, and EGF was not detected. It was concluded that upregulation of TGFα or FGF2 expression is not a pre‐requisite for enhanced testicular growth and increased Sertoli cell proliferation that occurs subsequent to hemicastration in the neonatal boar. Mol. Reprod. Dev. 75: 961–966, 2008. © 2008 Wiley‐Liss, Inc.
Modeling of resin infusion in vacuum assisted resin transfer molding
Authors: Song Young Seok , Youn Jae Ryoun
Published: February 2008

Resin infusion was modeled and analytic solutions were obtained for vacuum assisted resin transfer molding (VARTM). Compaction behavior of the fiber preform was examined experimentally and the influence of compressibility of the preform on the resin infusion was investigated mathematically. Flow front advancement through the preform was predicted by the analytic model proposed in the present study. The model provided pressure and thickness distributions of the region impregnated by the resin. For verification of the analytic solutions, a resin infusion experiment and a mold filling simulation for VARTM were performed and compared with the analytic ones. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers.
Impedance analysis and electromagnetic interference shielding effectiveness of conductive carbon black reinforced microcellular EPDM rubber vulcanizates
Authors: Mahapatra S.P. , Sridhar V. , Tripathy D.K.
Published: February 2008

The effect of processing variables (filler and blowing agent loadings) and operating variables (frequency and sample thickness) on the impedance and electromagnetic interference (EMI) shielding effectiveness of excess conductive carbon black reinforced solid and microcellular EPDM vulcanizates has been investigated. Increasing frequency showed a decrease in real part of complex impedance for both filler and blowing agent loadings, whereas the imaginary part showed a slight peak in the range of 9–10 GHz followed by a subsequent decrease. The measured impedance values were plotted as Nyquist plots (Argand diagrams) and a Resistor–Capacitance model was assumed. Increasing blowing agent loadings showed a marginal increase in the bulk resistivity, whereas increasing filler loadings had a significant decrease. The EMI shielding effectiveness increased monotonically with filler loading and showed a maximum of around 75 dB at 60 phr loadings, thus making them suitable for shielding applications. Increasing blowing agent loadings showed an increase in shielding effectiveness at low loadings (2 phr) whereas further increase showed a rapid decrease. This has been explained on the basis of formation of voids in the composite, which affect the absorbance capacity of the microcellular vulcanizates. However, the microcellular composites showed sufficiently high values in the range of 50–60 Db, thus making Vulcan XC 72 reinforced microcellular EPDM vulcanizates as ideal packaging material for EMI shielding applications. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers
Recycled poly(ethylene terephthalate) reinforced with basalt fibres: Rheology, structure, and utility properties
Authors: Kráčalík Milan , Pospíšil Ladislav , Šlouf Miroslav , Mikešová Jana , Sikora Antonín , Šimoník Josef , Fortelný Ivan
Published: February 2008

Utilization of recycled poly(ethylene terephthalate) (PET) as a matrix for composite materials prepared by continuous compounding is challenging from the environmental as well as industrial point of view. In our work, cut basalt fibers and talc powder of various compositions were used and their reinforcing effect on recycled PET was tested by rheology (Advanced Rheometric Expansion System), differential scanning calorimetry, and tensile experiments. The quality of filler dispersion in recycled PET matrix was investigated by scanning electron microscopy (SEM) and melt rheology. Processing and utility properties of composites were enhanced as compared with those of unfilled matrix. Higher melt elasticity, interfacial adhesion, and better mechanical performance of the composites were in a good agreement with the structure observed from SEM micrographs. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers
Effect of matrix chemical structure on the thermo‐oxidative stability of addition cure poly(imide siloxane) composites
Authors: Lincoln Jason E. , Morgan Roger J. , Curliss David B.
Published: February 2008

A series of addition cure poly(imide siloxane) resins were synthesized, incorporating various concentrations of α, ω‐bis(3‐aminopropyl) poly(dimethyl‐diphenylsiloxanes), and α, ω‐bis(p‐aminophenyl) poly(dimethylsiloxane) into the formulated imide oligomer. Both carbon and glass fiber textile laminates were fabricated using amic acid and polymerization of monomer reactants (PMR) approaches. The cured composite laminates were subjected to an accelerated thermo‐oxidative aging environment of 400°C for 100 h in air. Physical, thermal, and mechanical properties were evaluated to determine the structure‐oxidative stability interrelationships. In general, composite mechanical properties were found to increase with increasing siloxane concentration in the matrix. Composite thermo‐oxidative durability (measured via mass loss and mechanical property retention after oxidative aging) was improved through incorporation of diphenyl and diphenyl‐dimethyl siloxane segments into the imide oligomer backbone up to ∼35% by weight aminosiloxane. Oxidative stability was found to be mostly dependent on the degree of phenyl substitution on the silicon atoms in the siloxane blocks, as compared to the moiety attaching the amine groups to the siloxane block. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers
Effect of layered silicate on EPDM/EVA blend nanocomposite: Dynamic mechanical, thermal, and swelling properties
Authors: Acharya H. , Kuila T. , Srivastava S.K. , Bhowmick Anil. K.
Published: February 2008

Polymer blend nanocomposites have been developed by solution method using ethylene propylene diene terpolymer (EPDM), ethylene vinyl acetate (EVA‐45) copolymer, and organically modified layered silicate. Morphological investigation made by wide‐angle X‐ray diffraction and transmission electron microscopic analysis indicates intercalated structure of EPDM/EVA nanocomposites with partial disorder. Scanning electron microscopic studies exhibit the phase behavior of EPDM/EVA blend nanocomposites. Dynamic mechanical thermal analysis shows a significant increase in storage modulus in the rubbery plateau. The decrease in damping (tan δ) value and enhanced glass‐transition temperature (Tg) demonstrate the reinforcing effect of layered silicate in the EPDM/EVA blend matrix. The tensile modulus of these nanocomposites also showed a significant improvement with the filler content. The main chain scission of EPDM/EVA blend nanocomposites compared with the neat EPDM/EVA blend showed substantial improvement in thermal stability in nitrogen, whereas a sizeable increase is observed in air. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers
Mechanical behavior of highly filled natural CaCO3 composites: Effect of particle size distribution and interface interactions
Authors: Kaully T. , Siegmann A. , Shacham D.
Published: February 2008

The mechanical behavior of poly(di‐methyl siloxane) (PDMS) composites containing high volume fractions of natural CaCO3 particles of various particle size distributions was studied under tensile and oscillatory bending stresses, emphasizing the unique behavior of high filler loaded compositions. Composites containing the maximal possible solid loading of raw CaCO3 were investigated for the effect of fatty acids surface treatment. The elastic modulus increased with increasing filler loading, following Chantler's model for dental composites when correlated with the absolute filler volume fraction. Good fit to “traditional” models, e.g., Frankle‐Acrivos and Halpin‐Tsai, was obtained by correlating the modulus values with the volume fraction relative to the maximal possible filler loading. A master curve of different particle size distributions and filler levels composites was obtained by using the relative volume fraction values, illustrating the effect of particle packing characteristics on small deformation mechanical behavior. A minor increase in Tg was found in parallel to the appearance of a Tm relaxation peak at approximately −40°C. A peak temperature shift at Tm and a pronounced increase in this peak with increasing filler fraction was found as well. The changes in the melting transition are attributed to the constraints of the filler particles acting on the crosslinked melting polymer. Surface treatment with fatty acids significantly degraded the tensile properties. Interestingly, an increase of 4 vol% filler was enabled owing to the surface treatment, while restoring reasonable tensile properties. No significant effect was observed for excess of fatty acids resulting from physically adsorbed acids. Tan δ curves reveal low PDMS‐CaCO3 particles interactions, and mobility of the PDMS chains in the increased filler fraction as in the treated 64 vol% composite, both higher than those in the raw composite. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers
Electrical and mechanical properties of multi‐walled carbon nanotubes reinforced PMMA and PS composites
Authors: Mathur R.B. , Pande Shailaja , Singh B.P. , Dhami T.L.
Published: February 2008

The use of multi‐walled carbon nanotubes (MWCNT) as reinforcing material for thermoplastic polymer matrices, polymethyl methacrylate (PMMA), and polystyrene (PS) has been studied. MWCNT were synthesized by chemical vapor deposition (CVD) technique using ferrocene‐toluene mixture. As‐prepared nanotubes were ultrasonically dispersed in toluene and subsequently dispersed in PMMA and PS. Thin polymer composite films were fabricated by solvent casting. The effect of nanotube content on the electrical and mechanical properties of the nanocomposites was investigated. An improvement in electrical conductivity from insulating to conducting with increasing MWCNT content was observed. The carbon nanotube network showed a classical percolating network behavior with a low percolation threshold. Electromagnetic interference (EMI) shielding effectiveness value of about 18 dB was obtained in the frequency range 8.0–12 GHz (X‐band), for a 10 vol% CNT loading. An improved composite fabrication process using casting followed by compression molding and use of functionalized MWCNT resulted in increased composites strength. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers
Development and high stress abrasive wear behavior of milled carbon fiber‐reinforced epoxy gradient composites
Authors: Chand Navin , Naik A.M.
Published: February 2008

Milled carbon fiber‐reinforced polysulfide‐modified epoxy gradient composites have been developed. Density and hardness increases with the increase of carbon fiber content in the direction of centrifugal force, which shows the formation of gradient structure in the composite. High stress abrasive wear test was conducted on the gradient composites by using a Suga Abrasion Wear Tester. Abrasive wear rate reduced on increase of milled carbon fiber content from 0.15 to 1.66 vol%. Reduction in abrasive wear rate in milled carbon fiber‐reinforced epoxy gradient composites has been attributed to the increase of hardness, presence of random milled fibers, and debris of composite materials, which gave resistance and reduced wear rate. There is a small decrease in specific wear rate on adding 0.15 vol% milled carbon fibers. Further decrease of specific wear rate is observed on adding 0.45 vol% milled carbon fibers. After 3 N load, there is a decrease in specific wear rate behavior on adding 0.45 vol% carbon fibers, which further decreases on adding 0.60 vol% of carbon fibers. There is a remarkable decrease in specific wear rate up to 5 N load for 1.66 vol% milled carbon fiber‐reinforced composite. Reduction in specific wear rate on adding milled carbon fibers is based on the formation of debris, which remained intact in their respective positions due to the interfacial adhesion between milled carbon fibers and epoxy resin. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers
An acoustic emission study on the fracture behavior of continuous glass fiber/polypropylene composites based on commingled yarn
Authors: Wang Yantao , Dong Qingzhi , Zhang Degang , Xu Yongjun
Published: February 2008

The fracture behavior of continuous glass fiber reinforced polypropylene composites made of commingled yarn in the form of biaxial (±±45°) noncrimp warp‐knitted fabric, twill woven fabric, and swirl mat, respectively, was investigated by virtue of single edge notched tensile (SEN‐T) specimens. These composite laminates were manufactured by compression molding and cooled at two different rates (1°C/min and 10°C/min) during the last processing phase of the laminates. The failure mechanisms were studied by acoustic emission (AE) analysis. AE amplitude ranges corresponding to the individual failure modes have been identified. For biaxial noncrimp fabric reinforced materials, the failure mechanisms involved in the fracture procedure are governed by the interface related failure events. Higher cooling rate, which is accompanied by better fiber/matrix adhesion, results in not only the increase in the relative proportion of high‐amplitude failure events, but also the occurrence of a large quantity of fiber fracture events. For woven fabric and mat reinforced composites, fiber‐dominated failure mechanisms result in the higher fracture toughness when compared with biaxial noncrimp fabric composites. Under this circumstance, the change in cooling rate only results in the difference in the relative frequency of the individual failure modes. In addition, it is found out that the initiation fracture toughness of SEN‐T specimens can be easily assessed by marking the load value which corresponds to the first point of AE signals emitted stably in AE events‐displacement curves. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers
Effects of polymer molecular weight and filler particle size on flow behavior of wood polymer composites
Authors: Hristov Velichko , Vlachopoulos John
Published: February 2008

The influence of polymer matrix molecular weight and filler particle size on rheological properties and extrudate distortions of metallocene polyethylene (mPE)/wood flour (WF) composites has been investigated by rotational and capillary rheometers. It was found that at low shear rates smaller filler particles provide higher shear viscosity than the larger sized filler. At high shear rates and WF loadings above 30 wt%, the effect of particle size on the melt flow properties becomes negligible. The relative increase of the storage modulus with decreasing particle size is more pronounced in the case of low molecular weight polymer matrix than that in higher molecular weight polyethylene based composites. The wood filled polyethylenes exhibit extrudate surface defects, which are complex function of the shear rate, polymer matrix molecular weight, and filler particle size. Increasing the shear rate results in pressure oscillations and spurt‐flow. It was also observed that the evolution of the extrudate surface tearing is strongly dependent on the pressure during a single pressure oscillation cycle in the spurt flow regime. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers
Microencapsulation of ammonium polyphosphate: Preparation, characterization, and its flame retardance in polypropylene
Authors: Wu Kun , Wang Zhengzhou , Liang Haojun
Published: February 2008

Microencapsulated ammonium polyphosphate (MCAPP) with a melamine–formaldehyde (MF) resin coating layer was prepared by in situ polymerization. MCAPP was characterized by Fourier transform infrared, X‐ray photoelectron spectroscopy, and so on. The results show that the microencapsulation with MF resin leads to a decrease in the particles' size and water absorption. The flame retardant action and mechanism of MCAPP and ammonium polyphosphate (APP) in polypropylene are studied using limiting oxygen index (LOI) and UL 94 test, and their thermal stability is evaluated by thermogravimetric analysis. The LOI value of the PP/MCAPP composite at 30 wt% loading is 30.5%, whereas the corresponding value of the PP/APP composite is only 20%. Moreover, the LOI values of the PP/MCAPP/PER composites are higher than the ones of the PP/APP/PER composites. In the UL 94 test, the PP/MCAPP/PER composites with suitable ratios of MCAPP to PER can reach the V‐0 rating, and the best rating of the PP/APP/PER composites is V‐1. V‐1. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers
Synthesis and characterization of polyimide/multi‐walled carbon nanotube nanocomposites
Authors: Mo Te‐Cheng , Wang Hong‐Wen , Chen San‐Yan , Yeh Yun‐Chieh
Published: February 2008

Polyimide/multi‐walled carbon nanotube (PI‐MWNT) nanocomposites were fabricated by an in situ polymerization process. Chemical compatibility between the PI matrix and MWNTs is achieved by pretreatment of the carbon nanotubes in a mixture of sulfuric acid and nitric acid. The dispersion of MWNTs in the PI matrix was found to be enhanced significantly after acid modification. The glass transition (Tg) and decomposition (Td) temperature of PI‐MWNT nanocomposites were improved as the MWNT content increased from 0.5 to 15 wt%. The storage modulus of the PI/MWNT nanocomposites is nine times higher than that of pristine PI at room temperature. The tensile strength of PI doubles when 7 wt% MWNTs is added. The dielectric constant of the PI‐MWNT nanocomposites increased from 3.5 to 80 (1 kHz) as the MWNT content increased to 15 wt%. The present study demonstrates that enhanced mechanical properties can be obtained through a simple in‐situ polymerization process. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers
Effect of zirconium dioxide on crystallization and melting behavior of flame sprayed polyamide 1010
Authors: Li Yadong , Yan Fufeng , Qiang Kegang , Ma Yizhu , Cao Shaokui , Zhang Zhijun
Published: February 2008

The crystallization and melting behavior of flame sprayed Polyamide 1010 (PA1010) containing zirconium dioxide (ZrO2) were investigated using differential scanning calorimeter (DSC). ZrO2 has a heterogenous nucleation effect on PA1010, leading to a moderate increase in the crystallization temperature and a decrease in the supercooling temperature. A modified Avrami theory could be successfully used to well describe the early stages of non‐isothermal crystallization of PA1010 and its composite coatings. A study of the nucleation activity, which indicated the influence of the filler on the polymer matrix, revealed that the zirconium dioxide nanoparticles had a good nucleation effect on PA1010. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers.
Organic/inorganic hybrid nanospheres coated with palladium/P4VP shells from surface‐initiated atom transfer radical polymerization
Authors: Cheng Zhenping , Zhang Lifen , Zhu Xiulin , Kang E. T. , Neoh K. G.
Published: February 2008

Crosslinked poly(4‐vinylbenzyl chloride) (PVBC) nanospheres of about 160 nm were first synthesized by emulsion copolymerization of 4‐vinylbenzyl chloride (VBC) in the presence of a crosslinking agent, p‐divinylbenzene. Subsequent modification of the nanosphere surfaces via surface‐initiated atom transfer radical polymerization of 4‐vinylpyridine, using the VBC units of PVBC on the nanosphere surface as the macroinitiators, produced a well‐defined and covalently tethered poly(4‐vinylpyridine) (P4VP) shells of 24–27 nm in thickness. Activation of the P4VP shells in a PdCl2 solution, followed by reactions with CO or H2S gas, gave rise to the corresponding P4VP composite shells containing densely dispersed palladium metal or palladium sulfide nanoparticles. The chemical composition of the nanosphere surfaces at various stages of surface modification was characterized by X‐ray photoelectron spectroscopy. Field emission scanning electron microscopy and transmission electron microscopy were used to characterize the morphology of the organic/inorganic hybrid nanospheres coated with palladium/P4VP shells. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 2119–2131, 2008
Preparation of amphiphilic ternary block copolymers with PEO as the middle block and the effect of PEO position on the glass transition temperature (Tg) of copolymers
Authors: Zhang Yi , Pan Mugang , Liu Chao , Huang Junlian
Published: February 2008

The copolymer of polystyrene‐block‐poly(ethylene oxide)‐block‐poly (tert‐butyl acrylate) (PS‐b‐PEO‐b‐PtBA) was prepared, the synthesis process involved ring‐opening polymerization (ROP), nitroxide‐mediated polymerization (NMP), and atom transfer radical polymerization (ATRP), and 4‐hydroxyl‐2,2,6,6‐tetramethylpiperidinyl‐1‐oxy (HTEMPO) was used as parent compound. The PEO precursors with α‐hydroxyl‐ω‐2,2,6,6‐tetramethylpiperidinyl‐1‐oxy end groups(TEMPO‐PEO‐OH) were first obtained by ROP of EO using HTEMPO and diphenylmethylpotassium (DPMK) as the coinitiator. The TEMPO at one end of PEO chain mediated the polymerization of St using benzoyl peroxide as initiator. The resultant PS‐b‐PEO‐OH reacted further with 2‐bromoisobutyryl bromide and then initiated the polymerization of tBA in the presence of CuBr and PMDETA by ATRP. The ternary block copolymers PS‐b‐PEO‐b‐PtBA and intermediates were characterized by gel permeation chromatography, Fourier transform infrared, and nuclear magnetic resonance spectroscopy in detail. Differential scanning calorimetry measurements confirmed that the PS‐b‐PEO‐b‐PtBA with PEO as middle block can weaken the interaction between PS and PtBA blocks, the glass transition temperature (Tg) for two blocks were approximate to their corresponding homopolymers comparing with the PEO‐b‐PS‐b‐PtBA with PEO as the first block. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 2624–2631, 2008
Glycopeptide dendrimers, Part III—a review: Use of glycopeptide dendrimers in immunotherapy and diagnosis of cancer and viral diseases
Authors: Niederhafner Petr , Reiniš Milan , Šebestík Jaroslav , Ježek Jan
Published: February 2008

Glycopeptide dendrimers containing different types of tumor associated‐carbohydrate antigens (TN, TF, sialyl‐TN, sialyl‐TF, sialyl‐Lex, sialyl‐Lea etc.) were used in diagnosis and therapy of different sorts of cancer. These dendrimeric structures with incorporated T‐cell epitopes and adjuvants can be used as antitumor vaccines. Best results were obtained with multiantigenic vaccines, containing, e.g. five or six different TAAs. The topic of TAAs and their dendrimeric forms at molecular level are reviewed, including structure, syntheses, and biological activities. Use of glycopeptide dendrimers as antiviral vaccines against HIV and influenza is also described. Their syntheses, physico‐chemical properties, and biological activities are given with many examples. Copyright © 2008 European Peptide Society and John Wiley & Sons, Ltd.
Bacterial selectivity and plausible mode of antibacterial action of designed Pro‐rich short model antimicrobial peptides
Authors: Park Ka Hyon , Park Yoonkyung , Park II‐Seon , Hahm Kyung‐Soo , Shin Song Yub
Published: February 2008

To develop novel Pro‐rich model AMPs with shorter length and higher bacterial selectivity/therapeutic index (TI) than natural AMP, indolicidin, we synthesized a series of undodecapeptides derived from the sequence XXPXXPWXPXX‐NH2 (X indicates Leu or Lys) with different ratios of Lys and Leu residues. Several Pro‐rich model peptides (K7WP3, K6WL1P3, K5WL2P3‐1, K5WL2P3‐2, and K4WL3P3) had approximate 8‐ to 11‐fold higher bacterial selectivity/TI compared to indolicidin. These peptides selectively bind to negatively charged liposomes (EYPG/EYPG; 7:3, w/w) mimicking bacterial membranes. Their high selectivity to negatively charged phospholipids corresponds well with their high bacterial selectivity. Indolicidin showed almost complete depolarization of the cytoplasmic membrane of Staphylococcus aureus and dye‐leakage from negatively charged liposomes at 10 µM, whereas all of Pro‐rich model peptides had very little activity in these assays even at 80 µM, as observed in buforin 2. These results suggest that the ultimate target of our designed Pro‐rich model peptides is probably the intracellular components (e.g. protein, DNA or RNA) rather than the cytoplasmic membranes. Collectively, our designed Pro‐rich short model peptides appear to be excellent candidates for future development as a novel antimicrobial agent. Copyright © 2008 European Peptide Society and John Wiley & Sons, Ltd.