Search results for "Benzene"

Diffusiosmessungen an polymeren in lösung mittels tracer-technik

2007

A cell for measuring coefficients of diffusion and self-diffusion by tracer techniques is described. The cell consists of two Teflon disks and is of the rotational shearing type. The amount of polymer is minimal (about 0.1 ml. for both components). Labeled and unlabeled fractionated polymethacrylate of identical molecular weight distribution was used to determine diffusion coefficients in benzene and toluene. The classical optical measurement is impossible, for these solvents exhibit a refraction index very close to that of polymethacrylate. In acetone, where optical as well as tracer techniques are applicable, the measured diffusion coefficients of the two methods are in good agreement. Al…

The synthesis and condensation of oligo(phenylenevinylene)s with alkoxysilyl end groups

2002

Monodisperse alkoxylated oligo(phenylenevinylene)s with 3, 4, or 5 benzene rings were connected to reactive di- and triethoxysilanes, either directly or via flexible spacers. Aminopropylsilanes were condensed with stilbenoid aldehydes and subsequently reduced to amines, for the direct, rigid connection, the Heck reaction and also cross-metathesis with vinyl silanes proved to be successful routes. Hydrolysis of the ethoxysilanes leads to polymerisable cyclosiloxanes or curable three-dimensional networks with pendent chromophores.

Three 2,5-dialkoxy-1,4-diethynylbenzene derivatives

2008

2,5-Dieth­oxy-1,4-bis­[(trimethyl­silyl)ethyn­yl]benzene, C20H30O2Si2, (I), constitutes one of the first structurally characterized examples of a family of compounds, viz. the 2,5-dialk­oxy-1,4-bis­[(trimethyl­silyl)ethyn­yl]benzene derivatives, used in the preparation of oligo(phenyl­ene­ethynylene)s via Pd/Cu-catalysed cross-coupling. 2,5-Dieth­oxy-1,4-diethynylbenzene, C14H14O2, (II), results from protodesilylation of (I). 1,4-Diethynyl-2,5-bis­(hept­yloxy)benzene, C24H34O2, (III), is a long alk­yloxy chain analogue of (II). The molecules of compounds (I)–(III) are located on sites with crystallographic inversion symmetry. The large substituents either in the alkynyl group or in the benz…

The clinical relevance of low-density-lipoproteins size modulation by statins.

2006

The predominance of small, dense low density lipoproteins (LDL) has been accepted as an emerging cardiovascular risk factor by the National Cholesterol Education Program Adult Treatment Panel III; in fact, LDL size seems to be an important predictor of cardiovascular events and progression of coronary heart disease. Several studies have also shown that the therapeutical modulation of LDL size is of great benefit in reducing the risk of cardiovascular events. Hypolipidemic treatment is able to alter LDL subclass distribution and statins are currently the most widely used lipid-lowering agents. Statins are potent inhibitors of hydroxy-methyl-glutaryl-coenzyme A reductase, the rate-limiting en…

Response of yeast cells to high glucose involves molecular and physiological differences when compared to other osmostress conditions.

2015

Yeast cells can be affected by several causes of osmotic stress, such as high salt, sorbitol or glucose concentrations. The last condition is particularly interesting during natural processes where this microorganism participates. Response to osmostress requires the HOG (High Osmolarity Glycerol) pathway and several transcription factors, including Hot1, which plays a key role in high glucose concentrations. In this work, we describe how the yeast response to osmotic stress shows differences in accordance with the stress agent responsible for it. Compared with other conditions, under high glucose stress, delocalization of MAPK (Mitogen-Activated Protein Kinase) Hog1 is slower, induction of …

Untersuchung des Solvatationsgleichgewichts im ternären system Tetrachlormethan/Polymethylmethacrylat/Benzol durch kernmagnetische relaxation

1971

Im ternaren System CCl4/Polymethacrylate(PMMA)/Benzol tritt praferentielle Solvatation auf, Benzol ist in der Solvathulle des Polymeren angereichert. Es genugt eine Solvatationsgleichgewichtskonstante, um die praferentielle Solvatation bei variablen Konzentrationsverhaltnissen zu beschreiben. Gemessen wurde die Kernmagnetische Relaxationszeit T1 von Benzol in Abhangigkeit von der Polymerkonzentration. Der Vergleich mit analogen Messungen im System C6D6/PMMA/C6H6 ergibt fur die Solvatationsgleichgewichtskonstante K = (c32 · c10)/(c12 · c30) = 2,5 ± 0,5. Hierbei bedeuten: c10 die CCl4-Konzentrationen im „freien” Losungsmittel, c30 die Benzolkonzentrationen im „freien” Losungsmittel, c12 und c…

1977

The investigation of electron transfer and subsequent reactions of divinylidene compounds not capable of anionic homopolymerization was extended to 1,3-bis(1-phenylvinyl)benzene (2). A new method for the preparation of this compound is described. Its reaction with Li, Na, and K as electron transfer reagents in THF as solvent results in an increasing yield in polymeric combination products of the radical anions formed primarily with increasing reducing power of the alkali metal. The main product, however, in any case is the cyclic dimeric tetra-anion of 2, which upon protonation yields 1,4,11,14-tetraphenyl[4.4]metacyclophane (3).

NMR relaxation and solvation equilibrium in the ternary system CCl4-polymethylmethacrylate-benzene

2007

In the ternary system CCl4-PMMA-benzene, benzene is preferentially adsorbed in the solvation shell of the polymer. One solvation equilibrium constant allows a satisfactory description of the preferential solvation for a large range of solvent compositions. The nuclear magnetic relaxation time T1 of benzene protons was measured for different values of the polymer concentration. The measurements are compared with analogous measurements in the system C6D6-PMMA-C6H6 where no preferential solvation is to be expected. For the system CCl4-PMMA-benzene the resulting dimensionless solvation equilibrium constant is K = c32c10/c12c30 = 2.5 ± 0.5 where c10 is the CCl4 concentration in the “free” solven…

1H NMR-spektroskopische Untersuchungen zur Strukturaufklärung von Oligo(hydroxy-5-nitro-1,3-phenylen)methylen Verbindungen

1976

Die 1H NMR-Spektren von 51 Oligo(hydroxy-5-nitro-1,3-phenylen)methylen Verbindungen (17 Zwei-, 18 Drei-, 14 Vier- und 2 Funfkernverbindungen) wurden in Pyridin als Losungsmittel aufgenommen. Bei Verbindungen mit ortho-Nitrophenolbausteinen zeigten die Signale fur die Protonen der Methyl- bzw. Methylengruppen in allen Fallen charakteristische chemische Verschiebungen δ, so das eine eindeutige Unterscheidung zwischen Methylgruppen in para- (δ=2,09−2,15 p.p.m.) und ortho-Stellung (δ=2,22−2,28 p.p.m.) zur phenolischen Hydroxyl-Gruppe, sowie zwischen para-para- (δ=3,77−3,97 p.p.m.), ortho-para- (δ=4,02−4,12 p.p.m.) und ortho-ortho-Methylenbrucken (δ=4,21−4,32 p.p.m.) moglich war. Bei Verbindunge…

Sunitinib in patients with advanced hepatocellular carcinoma after progression under sorafenib treatment.

2010

<i>Objective:</i> To evaluate the safety and efficacy of sunitinib in patients with advanced hepatocellular carcinoma (HCC) after progression under sorafenib treatment. <i>Methods:</i> Sunitinib was administered at 37.5 mg daily (4-weeks-on/2-weeks-off schedule) after progression under sorafenib treatment. Adverse events (AEs) were assessed using NCI-CTCAE v3.0, and tumor response was evaluated according to RECIST. Data were analyzed retrospectively. <i>Results:</i> Eleven patients with metastatic disease were treated. Seven patients (64%) presented with no liver cirrhosis, including 3 patients with a history of liver transplantation. The first radiologic…