A communication interface of instrumentation modules and a SIM900 crate

An interface based on an AT89C51 microcontroller for modules of the SIM900 crate is described.     

New Method for Measuring the Rotation Inertia of a Single 4He Crystal

A new method for measuring the nonclassical rotation inertia of a helium single crystal is presented. This takes advantage of large crystals grown under conditions minimizing stresses and structural defects. High quality and large mass of crystals allow significantly increasing inertia signals and therefore sensitivity of measurements and accuracy of results. A method is tested at temperatures from 0.6 to 1.7 K in a frequency range of 100–1000 Hz. It is also used for studying internal friction in a helium single crystal.      

The Giant Growth of the Facets of 4He Crystal

No Heading Below the first and second roughening transitions the facets of a helium crystal demonstrate two qualitatively different regimes of growth. At small deviations from the equilibrium a crystal grows slowly via surface defects such as screw dislocations and Frank-Reed sources. The second regime is observed at high overpressurizations. A single crystal goes over into new state with the growth rates by several orders of the magnitude higher than the previous ones. The transition occurs simultaneously in both the basal and lateral facets. The time of formation of an anomalous state decreases drastically with the increase of the overpressurization and lies within the range of 0.1–200 ms. An average overpressurization. Dp₀ above which the anomalous state appears increases monotonically with the growth of temperature. The measurements of the facet growth rate immediately after a transition show that it reaches magnitudes up to 5 m/s at 20 mbar. Impurities of ³He with a concentration of 180 ppm retard the formation of the fast phase, namely, a boundary Dp₀(T) shifts to higher values. The features of this phenomenon (phase diagram, effect of impurity) are similar to the burst-like growth observed in the range of 2–250 mK at the (0001) facet without dislocations. Possibly, kinematical multiplication of steps plays a significant role in these effects, yielding a qualitatively new channel for the growth of an ideal facet.PACS numbers: 67.80.–s, 68.45.–v     

Instability of a Crystal 4He Facet in the Field of Gravity

We analyze here the analog of the Rayleigh instability in the field of gravity for the superfluid?Ccrystal ⁴He interface provided that the heavier ⁴He crystal phase occupies the space over the lighter superfluid phase. We find that the conditions and onset of the gravitational instability are different in kind above and below the roughening transition temperature when the crystal ⁴He surface is in the rough or in the smooth faceted state, respectively. In the rough state of the surface the gravitational instability is fully analogous to the classical case of the fluid?Cfluid interface. In contrast, in the case of the crystal faceted surface the onset of the gravitational instability is associated with surmounting some potential barrier. The potential barrier results from nonzero magnitude of the facet step energy. The size and the tilting angle of the crystal facet are also important parameters for developing the instability. The initial stage of the instability can be described as a generation of crystallization waves at the superfluid?Ccrystal interface. In particular, we discuss the experiments (Demaria et al. in J. Low Temp. Phys. 89:385, 1992; Tsymbalenko in Fiz. Nizk. Temp. 21:162, 1995; Tsymbalenko in Low Temp. Phys. 21:120, 1995) which may concern the gravitational instability of the superfluid-crystal ⁴He interface.     

Effects of infant formula feeding on the distribution of copper in the body of 8-day-old rats

The oxidase activity of ceruloplasmin (Cp, EC 1.16.3.1), the content of immunoreactive Cp and copper ion concentration were measured in the serum of eight day-old rats receiving either breast feeding (control group) or commercial nutritive mixture which has been recommended for the newborn children beginning from zero age (experimental group). It was shown that the artificial feeding caused almost 3-fold increase of Cp oxidase activity and copper content in the serum when compared to age-matched controls. No changes in the copper content per Cp molecule were observed. Dot-hybridization of the total liver polyribosomal RNA with Cp [32P]cDNA showed that the increased Cp level in the blood of the rats of experimental group correlated well with the level of expression of Cp gene. The copper content in the liver of experimental rats was two times lower that in control animals while no differences was found in the brain copper content between two groups of rats. The role of the regulation of Cp gene expression in the lactating mammary gland and of milk Cp in the copper homeostasis in the newborn body is discussed.     

Automatic refilling with liquid nitrogen under control of the microcontroller

A design of the module controlling the cryostat filling with liquid nitrogen is presented. It is capable of operating in three modes: (i) indication of level sensor readouts, (ii) automatic maintenance of the liquid nitrogen level; and (iii) timer-based filling.     

Diffusion mechanism in the quantum decay of metastable3He-4He mixtures at low temperatures

We study the quantum phase-separation kinetics of a supersaturated liquid mixture at temperatures down to absolute zero. The energy dissipation effect of diffusion is incorporated into the calculation of the nucleation rate in normal and superfluid liquid mixtures. Unlike single-component systems, diffusion is the principal process which governs both the quantum nucleation rate and supercritical droplet growth rate in mixtures near the demixing curve. The low temperature phase-separation experiments in supersaturated liquid³He-⁴He mixtures of³He-dilute phase are analyzed and discussed. The critical degree of metastability and at the same time the critical droplet radius are shown to be temperature-independent below about 80 mK, suggesting the temperature of the thermal-to-quantum crossover to be of the same order of magnitude. The critical radius of a demixed droplet is estimated as about 20 Å, being within reasonable values.     

A low-power current regulator for low-temperature thermometers

A battery-supplied current regulator for low-temperature thermometers is described. The regulator operates in the range 1–10 µA and consumes a current of 0.12 mA.__________Translated from Pribory i Tekhnika Eksperimenta, No. 2, 2005, p. 146.Original Russian Text Copyright © 2005 by Tsymbalenko.     

Multiprocessor-Based Measuring Controller for Automatic Measurements on the Windows Platform

A controller for measurements and experiments control, which is connected via a serial port to the host computer, is described. It can operate with programs functioning on the Windows platform. The module has 8 analog inputs, 4 analog outputs, and an 8-bit bidirectional port.