Can the tardigrade Hypsibius dujardini survive in the absence of the geomagnetic field?

Earth's geomagnetic field has undergone critical changes in the past. Studies on the influence of the magnetic field on Earth's organisms are crucial for the understanding of evolution of life on Earth and astrobiological considerations. Numerous studies conducted both on plants and animals confirmed the significant influence of the geomagnetic field on the metabolism of living organisms. Water bears (Tardigrada), which are a mong the most resistant animals due to their cryptobiotic abilities, show significant resistance to a number of environmental stressors, but the influence of the geomagnetic field on their fitness has not been addressed before. In our studies, we used eutardigrade Hypsibius dujardini to analyse whether isolation from the geomagnetic field had an effect on mortality. We found that Hypsibius dujardini specimens demonstrated relatively high mortality during anhydrobiosis, also in control groups exposed to the normal geomagnetic field. Moreover, similar mortality was observed in anhydrobiotic specimens isolated from the geomagnetic field. However, a significant difference was noted between tardigrade survival and the moment of their isolation from the geomagnetic field. In particular, tardigrade mortality substantially increased in absence of a magnetic field during the process of entering anhydrobiosis and returning to active life. Our results suggest that these processes rely on complex metabolic processes that are critically influenced by the geomagnetic field.

Tailoring magnetic anisotropy gradients by ion bombardment for domain wall positioning in magnetic multilayers with perpendicular anisotropy.

Graded anisotropy magnetic materials possess a coercive field changing laterally with position. A simple fabrication procedure to produce such an anisotropy gradient in a polycrystalline Au/Co layer system without lateral thickness variation and with perpendicular magnetic anisotropy, prototypical for a large variety of thin film systems, is shown. The procedure uses light-ion bombardment without the use of a mask. Magnetization reversal in this polycrystalline layer system takes place by unidirectional movement of a single domain wall only in regions with larger anisotropies and anisotropy gradients. In this anisotropy/anisotropy gradient regime, the domain wall is oriented perpendicular to the coercive field gradient, and it can be positioned along the gradient by an appropriate magnetic field pulse. For smaller anisotropies/anisotropy gradients, the natural anisotropy fluctuations of the polycrystalline layer system induce magnetization reversal dominated by domain nucleation. PACS: 75.30.Gw; 75.70.Cn; 75.60.Ch.

Colloidal domain lithography in multilayers with perpendicular anisotropy: an experimental study and micromagnetic simulations.

Currently, much attention is being paid to patterned multilayer systems in which there exists a perpendicular magnetic anisotropy, because of their potential applications in spintronics devices and in a new generation of magnetic storage media. To further improve their performance, different patterning techniques can be used, which render them suitable also for other applications. Here we show that He(+) 10 keV and Ar(+) 100 keV ion bombardment of (Ni(80)Fe(20)-2 nm/Au-2 nm/Co-0.6 nm/Au-2 nm)(10) multilayers through colloidal mask enables magnetic patterning of regularly arranged cylindrical magnetic domains, with perpendicular anisotropy, embedded in a non-ferromagnetic matrix or in a ferromagnetic matrix with magnetization oriented along the normal. These domains form an almost perfect two-dimensional hexagonal lattice with a submicron period and a large correlation length in a continuous and flat multilayer system. The magnetic anisotropy of these artificial domains remains unaffected by the magnetic patterning process, however the magnetization configuration of such a system depends on the magnetic properties of the matrix. The micromagnetic simulations were used to explain some of the features of the investigated patterned structures.

Colloidal domain lithography for regularly arranged artificial magnetic out-of-plane monodomains in Au/Co/Au layers.

Regularly arranged magnetic out-of-plane patterns in continuous and flat films are promising for applications in data storage technology (bit patterned media) or transport of individual magnetic particles. Whereas topographic magnetic structures are fabricated by standard lithographical techniques, the fabrication of regularly arranged artificial domains in topographically flat films is difficult, since the free energy minimization determines the existence, shape, and regularity of domains. Here we show that keV He(+) ion bombardment of Au/Co/Au layer systems through a colloidal mask of hexagonally arranged spherical polystyrene beads enables magnetic patterning of regularly arranged cylindrical magnetic monodomains with out-of-plane magnetization embedded in a ferromagnetic matrix with easy-plane anisotropy. This colloidal domain lithography creates artificial domains via periodic lateral anisotropy variations induced by periodic defect density modulations. Magnetization reversal of the layer system observed by magnetic force microscopy shows individual disc switching indicating monodomain states.

The rate of loss of eyelid reflex following thiopental administration in hypo- and hypergonadism in rabbits.

BACKGROUND: The aim of this research was to explain whether different hormonal conditions caused by disturbed concentrations of estrogens and progesterone might lead to alteration of CNS reaction following administration of the hypnotic agent thiopental. The investigated factor was the rate of loss of the eyelid reflex after intravenous thiopental administration, since this corresponds with loss of consciousness. MATERIAL/METHODS: The investigation was performed in 24 sexually mature female Chinchilla rabbits divided into 4 groups of 6 rabbits each. The animals were oophorectomized (hypoprogesterone/hypoestrogen), hyperestrogen (sham surgery plus estradiol injections), hyperprogesterone (sham surgery plus 17 alpha-hydroxyprogesterone injections), or normal (sham surgery). Twelve weeks later, thiopental (40 mg/ml) was infused through the intravenous cannula at a constant rate (90 ml/hour) until loss of the eyelid reflex, at which time blood was sampled for determination of thiopental, b-estradiol, progesterone and 17 alpha-hydroxyprogesterone concentrations. The ANOVA and Tukey tests were applied in statistical analysis (p=0.05). RESULTS: Hyperprogesterone rabbits lost consciousness faster (138 +/- 34.6 sec), at a lower plasma thiopental concentration (46.3 +/- 6.6 microg/ml), and required less thiopental (24.63 +/- 6.44 mg/kg) than controls; hypoprogesterone rabbits lost consciousness slower (207.5 +/- 30.9 sec), at a higher plasma thiopental concentration (129.2 +/- 24.9 microg/ml), and required more thiopental (38.51 +/- 2.33 mg/kg) than controls. The time of sleep induction in the control group was 190 +/- 25.7 sec.; the serum thiopental concentration was 77.8 +/- 13.9 microg/ml, and the total thiopental consumption was 35.8 +/- 3.51 mg/kg. Estrogen status has no effect. CONCLUSIONS: Various hormonal states are accompanied by different CNS reactions to thiopental. Among the studied groups of sex steroids, only progestins significantly modify the CNS response to barbiturate infusion.