Search results for "TRES"

Deformation recovery behaviour of a solid polymer after tensile yielding

1987

In this work the deformation recovery behavior of an amorphous polymer after large tensile deformation is studied at different temperatures. The effect of three parameters other than temperature has been pointed out in previous works (1–3). The data here presented indicate that the influence of all parameters, including temperature, on recovery behavior can be related to the residual stress, σ *, at the beginning of recovery test. This suggests to plot the recovery versus time curves, relative to different sets of parameters including temperature, by means of the same normalizing groups which were adopted in (2), thus shifting all curves towards a single master curve.

A new equipment to measure the combined effect of humidity, temperature, mechanical stress and UV exposure on the creep behaviour of polymers

2008

To be able to study and predict the physical properties of a polymeric material under different environmental conditions is very important. Moisture, UV irradiation, thermal and mechanical stresses can dramatically change the characteristics of the material and hinder some specific applications. In this work, a new equipment able to perform creep tests under different environmental conditions (temperature, humidity, stress) is presented. Some preliminary results are also presented using a sample of polyamide 6. As this polymer is sensitive to all these variables, it is appropriate to verify the effectiveness of the new instrument.

Elongational flow of dilute polymer solutions

1974

In this work, elongational viscosity data obtained for dilute solutions of Separan NP 20 in glycerol, are presented. The data are taken under transient stress conditions with two different experimental techniques.

Thermo- and photo-oxidative stability and improved processability of polyamide stabilized with a new functional additive

2005

During processing polyamides can undergo thermo-mechanical degradation due to the mechanical stress and to the high temperature applied to the melt. Degradation can occur also during the polyamides lifetime due to many driving forces, like temperature, ultraviolet radiations, etc. The mechanisms of degradation are not well understood and the stabilization with usual stabilizers, like phenol antioxidants, is not so efficient as for other classes of polymers. The aim of this work is the study of the effects of the addition of a new multifunctional additive on the processing and on the thermo- and photo-stabilization of polyamide-6. This additive is able to prevent the thermo-mechanical degrad…

Regulation of Human ALDH-2 Activity by Electrophiles – Implications for Organic Nitrate Induced Tolerance, Oxidative Stress and Reactive Fatty Acid M…

2010

Chronic Lymphocytic Leukemia: Correlations Between Oxidative Stress Metabolism and Cytogenetic Subgroups

2008

Abstract The chronic lymphocytic leukemia (B cell-CLL) is a heterogeneous lymphoproliferative disorder susceptible to oxidative stress. The excessive production of reactive oxygen intermediates above the capability of naturally produced antioxidants may result in the instability of essential macromolecules, and represents the molecular basis of many diseases including cancer. Highly reactive radicals interact with DNA inducing a multitude of oxidative modifications, and are implicated in mutagenesis due to misreplication of the damaged base 8-oxo-2′-deoxiguanosine (8-oxo-dG). Furthermore, protooncogene activation and/or tumor suppressor gene inhibition has been reported as a consequence of …

Nitrate Reductase Activity of Mitochondrial Aldehyde Dehydrogenase (ALDH-2) as a Redox Sensor for Cardiovascular Oxidative Stress

2009

In 2002, mitochondrial aldehyde dehydrogenase (ALDH-2) was identified as an organic nitrate bioactivating enzyme. This so-called nitrate reductase activity denitrates nitroglycerin (glycerol trinitrate) to its 1,2-glycerol dinitrate metabolite and nitrite. This reaction relies on reduced thiols at the active site of the enzyme and on the presence of reduced dithiols as the electron source. During bioconversion of nitroglycerin, and also in the presence of reactive oxygen and nitrogen species, the active site thiols of ALDH-2 are oxidized and the enzyme looses its activity. We, therefore, speculated that ALDH-2 activity could be a useful marker for cardiovascular oxidative stress. Indeed, th…

Oxidative stress and enzymatic antioxidant mechanisms in essential hypertension

2001

Molecular response to TBT stress in marine sponge Suberites domuncula: proteolytical cleavage and phosphorylation of KRS_SD protein kinase

2003

Abstract Marine sponges as sessile filter feeders are inevitably under a constant influence of changes in their environment. Mediation of extracellular signals and regulation of cellular response to environmental stress is a key function of cellular protein kinases. Expression, proteolytical cleavage and phosphorylation of stress-responsive KRS_SD protein kinase, in control and tributyl-tin (TBT) treated sponges were investigated. In control sponge, two KRS_SD proteins were expressed: KRS_SD1 (54 kDa) corresponding to KRS_SD calculated molecular weight, and KRS_SD2 (50 kDa). Exposure of sponges to TBT resulted in alteration of KRS_SD1 and KRS_SD2 expression levels and their phosphorylation …

Age-related changes in antioxidant status and oxidative damage to lipids and dna in mitochondria of rat liver

2005

To investigate the correlation between oxidative stress and mitochondrial damage with aging, antioxidant system, levels of oxidative DNA damage and as an index of the loss of plasma membrane integrity lipid peroxidation and membrane potential were studied. Results showed that the activities of antioxidant enzymes superoxide dismutase (SOD) and catalase significantly decreased during aging, however glutathione peroxidase (GSH-PX) increased in the aged mitochondria and glutathione (GSH) did not change during aging. No statistical difference was observed in the lipid peroxidation of mitochondria between young and old animals. The level of oxidative DNA damage (measured as 8oxo-dG) tended to in…