50 research outputs found
Low Temperature Measurements by Infrared Spectroscopy in CoFeO Ceramic
In this paper results of new far-infrared and middle-infrared measurements
(wavenumber range of 4000cm-1 - 100cm-1) in the range of the temperature from
300K to 8K of the CoFe2O4 ceramic are presented. The bands positions and their
shapes are the same in the wide temperature range. The quality of the sample
was investigated by X-ray, EDS and EPMA studies. The CoFe2O4 reveals the cubic
structure (Fd-3m) in the temperature range from 85K to 360 K without any traces
of distortion. On the current level of knowledge the polycrystalline CoFe2O4
does not exhibit phase transition in the temperature range from 8 K to 300 K.Comment: 10 pages, 6 figure
Oviposition preference of the neotropical brown stink bug Euschistus heros on artificial substrates of different colors
Effects of sleep deprivation on neural functioning: an integrative review
Sleep deprivation has a broad variety of effects on human performance and neural functioning that manifest themselves at different levels of description. On a macroscopic level, sleep deprivation mainly affects executive functions, especially in novel tasks. Macroscopic and mesoscopic effects of sleep deprivation on brain activity include reduced cortical responsiveness to incoming stimuli, reflecting reduced attention. On a microscopic level, sleep deprivation is associated with increased levels of adenosine, a neuromodulator that has a general inhibitory effect on neural activity. The inhibition of cholinergic nuclei appears particularly relevant, as the associated decrease in cortical acetylcholine seems to cause effects of sleep deprivation on macroscopic brain activity. In general, however, the relationships between the neural effects of sleep deprivation across observation scales are poorly understood and uncovering these relationships should be a primary target in future research
Surface magnetism in iron, cobalt, and nickel
We have calculated magnetic moments, work functions, and surface energies for several of the most closely packed surfaces of iron, cobalt, and nickel by means of a spin-polarized Greenâs-function technique based on the linear muffin-tin orbitals method within the tight-binding and atomic sphere approximations. We find enhanced spin moments at all the surfaces considered except for Ni fcc(111), where the moment at the surface reverts to its bulk value. This is in close agreement with earlier slab calculations. In addition, we find that the calculated work functions and surface energies agree with experimental values to within 10%, which may be considered most satisfactory in view of the computational efficiency of the Greenâs function technique. Exchange and correlation have been treated wihtin the local spin-density approximation and we have considered three different parametrizations of the original many-body data. We find that the calculated work functions depend as much on the choice of this parametrization as on the effect of spin polarization
The structure of temperate yellowjacket communities is affected by land development and loss of forest cover
Pharmacogenetics of Modafinil after sleep loss: Catechol-O-methyltransferase genotype modulates waking functions but not recovery sleep
Sleep loss impairs waking functions and is homeostatically compensated in recovery sleep. The mechanisms underlying the consequences of prolonged wakefulness are unknown. The stimulant modafinil may promote primarily dopaminergic neurotransmission. Catechol-O-methyltransferase (COMT) catalyzes the breakdown of cerebral dopamine. A functional Val158Met polymorphism reduces COMT activity, and Val/Val homozygous individuals presumably have lower dopaminergic signaling in the prefrontal cortex than do Met/Met homozygotes. We quantified the contribution of this polymorphism to the effects of sleep deprivation and modafinil on subjective state, cognitive performance, and recovery sleep in healthy volunteers. Two-time 100 mg modafinil potently improved vigor and well-being, and maintained baseline performance with respect to executive functioning and vigilant attention throughout sleep deprivation in Val/Val genotype subjects but was hardly effective in subjects with the Met/Met genotype. Neither modafinil nor the Val158Met polymorphism affected distinct markers of sleep homeostasis in recovery sleep. In conclusion, dopaminergic mechanisms contribute to impaired waking functions after sleep loss