Search results for "plastic"

Step growth polymerization via tandem ene and diels-alder reactions

1997

In contrast to other electron deficient enophiles or dienophiles which react with 1,4-cyclohexadiene (1,4-CHD) under aromatization, 1,2,4-triazoline-3,5-diones react in a defined reaction sequence. In a first step the 1,4-cyclohexadiene reacts via an ene-reaction. The intermediately formed substituted 1,3-cyclohexadiene immediately reacts in a Diels-Alder reaction. The regiochemistry of the Diels-Alder reaction is controlled by the solvent polarity. This reaction sequence can be used to synthesize polymers. Low-molar-mass model compounds were synthesized to elucidate the stereochemistry of the polymers. By varying the bistriazolinedione, polymers with backbones of different rigidity are ava…

Effect of catalyst composition on chain-end-group of polyethylene produced by salen-type complexes of titanium, zirconium, and vanadium

2010

The Mechanism of Diene Polymerisation by Organolanthanide Catalysts Deduced from Microwave Experiments

2005

Isoprene polymerisation performed under microwave irradiation with [Nd(BH 4 ) 3 (THF) 3 ]/Mg(Bu) 2 and [Nd-(BH 4 ) 3 (THE) 3 ]/Al(Et) 3 showed an enhancement in reactivity, with selectivity being only slightly modified. An explanation of the observed effect is proposed based on our current knowledge of the catalytic mechanism and by considering the alkylated complex as an ion pair. An analogy is proposed with the pseudoanionic polymerisation of oxygenated monomers. Finally, depolymerisation is observed under microwave irradiation at high temperature.

Chain-extending of Hydroxytelechelic Polybutadiene: Synthesis and Characterization

2010

Extension of hydroxytelechelic polybutadiene oligomers ( 3200 g/mol) is performed in mild conditions, in order to avoid backbone modifications, using succinic anhydride or methylenedicyclohexyl diisocyanate. The two routes present significative extension of the initial oligomers. Extension through the anhydride route, in the presence of DCC and DMAP, leads to new hydroxytelechelic oligomers ( 8000 g/mol). Extension through the diisocyanate route, catalyzed by DBTL at 65°C leads to hydroxytelechelic oligomers of higher average molecular weight ( 20000 g/mol). New materials are characterized by FTIR/1H-NMR and changes in their Tg according to , are discussed. The influence of reaction time on…

Entrectinib: a potent new TRK, ROS1, and ALK inhibitor

2015

Abstract: Introduction: Receptor tyrosine kinases (RTKs) and their signaling pathways, control normal cellular processes; however, their deregulation play important roles in malignant transformation. In advanced non-small cell lung cancer (NSCLC), the recognition of oncogenic activation of specific RTKs, has led to the development of molecularly targeted agents that only benefit roughly 20% of patients. Entrectinib is a pan-TRK, ROS1 and ALK inhibitor that has shown potent anti-neoplastic activity and tolerability in various neoplastic conditions, particularly NSCLC. Areas covered: This review outlines the pharmacokinetics, pharmacodynamics, mechanism of action, safety, tolerability, pre-cl…

Targeted Therapy Modulates the Secretome of Cancer-Associated Fibroblasts to Induce Resistance in HER2-Positive Breast Cancer

2021

The combination of trastuzumab plus pertuzumab plus docetaxel as a first-line therapy in patients with HER2-positive metastatic breast cancer has provided significant clinical benefits compared to trastuzumab plus docetaxel alone. However, despite the therapeutic success of existing therapies targeting HER2, tumours invariably relapse. Therefore, there is an urgent need to improve our understanding of the mechanisms governing resistance, so that specific therapeutic strategies can be developed to provide improved efficacy. It is well known that the tumour microenvironment (TME) has a significant impact on cancer behaviour. Cancer-associated fibroblasts (CAFs) are essential components of the…

Novel therapeutic targets in esophageal cancer: impact of chemokine receptor CXCR4

2007

Ines Gockel†, Carl C Schimanski, Markus Moehler & Theodor Junginger †Author for correspondence Johannes GutenbergUniversity of Mainz, Department of General and Abdominal Surgery, Langenbeckstr. 1, 55131 Mainz, Germany Tel.: +49 6131 177 291; Fax: +49 6131 176 630; gockel@ach.klinik.unimainz.de ‘The interaction between esophageal cancer-expressed CXCR4 and SDF-1α may have a key role in directing malignant cells to ‘homing’ organs ... thus, this mechanism may account for metastasis.’

Characterization of a Naturally Occurring Breast Cancer Subset Enriched in Epithelial-to-Mesenchymal Transition and Stem Cell Characteristics

2009

Abstract Metaplastic breast cancers (MBC) are aggressive, chemoresistant tumors characterized by lineage plasticity. To advance understanding of their pathogenesis and relatedness to other breast cancer subtypes, 28 MBCs were compared with common breast cancers using comparative genomic hybridization, transcriptional profiling, and reverse-phase protein arrays and by sequencing for common breast cancer mutations. MBCs showed unique DNA copy number aberrations compared with common breast cancers. PIK3CA mutations were detected in 9 of 19 MBCs (47.4%) versus 80 of 232 hormone receptor–positive cancers (34.5%; P = 0.32), 17 of 75 HER-2–positive samples (22.7%; P = 0.04), 20 of 240 basal-like c…

SAHA/TRAIL combination induces detachment and anoikis of MDA-MB231 and MCF-7 breast cancer cells

2012

Abstract SAHA, an inhibitor of histone deacetylase activity, has been shown to sensitize tumor cells to apoptosis induced by TRAIL, a member of TNF-family. In this paper we investigated the effect of SAHA/TRAIL combination in two breast cancer cell lines, the ERα−positive MCF-7 and the ERα−negative MDA-MB231. Treatment of MDA-MB231 and MCF-7 cells with SAHA in combination with TRAIL caused detachment of cells followed by anoikis, a form of apoptosis which occurs after cell detachment, while treatment with SAHA or TRAIL alone did not produce these effects. The effects were more evident in MDA-MB231 cells, which were chosen for ascertaining the mechanism of SAHA/TRAIL action. Our results show…

Reconstruction of the face with skin-grafted muscle flaps: Optimizing the aesthetic outcome

2011

BACKGROUND: Reconstruction of large defects in the temporal region can be performed with skin grafts or pedicled or free flaps. Results are often not optimal because of the patch of a skin graft, lack of availability of local flaps, and distant skin from free flaps. A technique for reconstruction of these defects with local tissue is presented in this article that uses superficial musculoaponeurotic system (SMAS) plication to allow wide advancement of a cervicofacial flap. METHODS: Once the defect is outlined, a face-lift-like skin incision is used to raise the flap. The SMAS is plicated with two purse-string sutures that relieve tension on the flap and allow maximal advancement. Thirteen f…