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D Thomsen

Publications and source records attributed to D Thomsen.

9 recordsLinked to original sources
PubMed2000

Vogel-fulcher dependence of relaxation rates in a nematic monomer and elastomer

Dielectric relaxation spectroscopy is used to study the relaxation processes in a nematic monomer and the corresponding cross-linked polymer nematic liquid crystal (elastomer). In the frequency window 10 mHz to 2 GHz the monomer liquid crystal shows a single relaxation whereas the polymer exhibits three relaxation processes, two of which are quantitatively analyzed. The temperature dependence of relaxation times in both the monomer and polymer follows a Vogel-Fulcher behavior. The relaxation processes are identified with specific molecular motions and activation energies are calculated in a linear approximation for comparison with literature data.

Journal Article↗
PubMed1997

Vanadates form insoluble complexes with histones.

Vanadium oxoanions are known to have a variety of physiological effects including insulin-like activity, inhibition of phosphotyrosine phosphatases, as well as direct interactions with a variety of cellular proteins, such as microtubules. In this study, vanadate was found to form insoluble complexes with histones, as well as other positively charged proteins, in a concentration dependent fashion. This interaction occurred over a 0.5-10 mM range which corresponds to the concentration range required for many of vanadate's known physiological effects. Results from precipitation experiments using vanadate solutions with or without the yellow-orange decavanadate indicated that the decamer form is primarily responsible for this precipitation. Vanadate was able to selectively precipitate histones from soluble chromatin as well as from a soluble bacterial protein extract to which a low concentration of histones had been added. Vanadate was also able to effectively precipitate histone from solutions as low as 0.006 mg/mL histone. Thus, the selective precipitation of histones and other positively charged proteins by vanadate can be utilized as a tool for protein purification. In addition, this interaction may provide insight into the mechanisms for the physiological effects of vanadate.

Animals↗
PubMed1991

Physiological responses during aerobic dance of individuals grouped by aerobic capacity and dance experience.

This study examined the effects of aerobic capacity (peak oxygen uptake) and aerobic dance experience on the physiological responses to an aerobic dance routine. The heart rate (HR) and VO2 responses to three levels (intensities) of aerobic dance were measured in 27 women. Experienced aerobic dancers (AD) (mean peak VO2 = 42 ml.kg-1.min-1) were compared to subjects with limited aerobic dance experience of high (HI) (peak VO2 greater than 35 ml.kg-1.min-1) and low (LO) (peak VO2 less than 35 ml.kg-1.min-1) aerobic capacities. The results indicated the LO group exercised at a higher percentage of peak heart rate and peak VO2 at all three dance levels than did either the HI or AD groups (HI = AD). Design of aerobic dance routines must consider the exercise tolerance of the intended audience. In mixed groups, individuals with low aerobic capacities should be shown how and encouraged to modify the activity to reduce the level of exertion.

Adult↗
PubMed1979

Visual modulation of otolith-dependent units in cat vestibular nuclei.

Vestibular nucleus units responding to translational self-motion are shown to respond also to translational movement of a large visual field. These visual-vestibular interactions in otolith-dependent units are similar to those found in canal-related units and could provide the basis for linearvection.

Animals↗
PubMed1977

Depriving rats of REM sleep: the identification of a methodological problem.

Several studies that used Jouvet's platform-in-the-water technique to deprive rats of REM sleep are reviewed. It is observed that a consistent feature of the design of these studies was to ignore the ratio between the size of the animal and the diameter of the platform when the REM deprivation was manipulated. Some contradictory studies are considered, and it is shown that the discrepant outcomes in the literature could be the result of inattention to that ratio.

Animals↗