High-temperature stability of low-oxygen silicon carbide fiber heat-treated under different atmosphere

The effects of heat-treating atmosphere on the thermal stability of low-oxygen silicon carbide fiber were investigated. Heat-treatment of EB-cured PCS fiber were conducted at 1573 K in argon, nitrogen or vacuum of 10^–6 atm. Subsequently the fibers were exposed to 1873 K in argon. The strength of fibers were strongly influenced by the heat-treating atmosphere. When heat-treated in nitrogen, the fibers absorbed nitrogen. High-temperature exposure caused severe degradation of strength owing to the decomposition of silicon oxycarbonitride phase. When heat-treated in vacuum, the fiber surface was smooth and pore-free, minimizing the degradation of strength at high temperature.     

Performance improvement of a two-stage GM cryocooler by use of Er(Ni0.075Co0.925)2 magnetic regenerator material

A newly developed magnetic regenerator material Er(Ni_0.075Co_0.925)₂, having high specific heat at temperatures from 10 to 20 K, has been tested inside the second regenerator of a two-stage GM cryocooler. Different working conditions have been examined: four Er(Ni_0.075Co_0.925)₂/Pb material ratios, three displacer reciprocating speeds, and two cryocooler stroke lengths. In the best working conditions, the experimental results show a cooling power improvement up to 15% over the whole temperature range from 10 to 20 K compared to that of the same GM cryocooler employing only lead.     

RETRACTED ARTICLE: Single-Phase <Emphasis Type="Italic">β</Emphasis>-Zn<Subscript>4</Subscript>Sb<Subscript>3</Subscript> Prepared by a Mechanical Grinding Method

Single-phase β-Zn₄Sb₃ materials were prepared by mechanical grinding (MG). Source materials for the Zn₄Sb₃ ingots were prepared using three different processes after the direct melting of constituent elements. In process 1, the ingot was obtained by quenching the melt in water within an evacuated quartz ampoule. In process 2, the ingot was heat-treated for 100 h at 723 K after process 1. In process 3, the ingot was heat-treated for a total of 200 h in two stages at 723 K and 673 K after process 1. The resultant ingots were mechanically ground and sintered at 623 K by hot pressing. The sintered materials were characterized by x-ray diffraction, differential thermal analysis (DTA), and thermoelectric property measurements. The thermal conductivity of the sintered materials was 0.88 W m⁻¹ K⁻¹ at room temperature, being slightly lower than that reported for the materials prepared by a conventional method. Results indicate that the dimensionless figure of merit of the single-phase β-Zn₄Sb₃ ranged from 1.06 to 1.31 at 573 K.     

Lorentzian force type fibre-optic AC magnetic sensor realisingfrequency-independent sensitivity

A Lorentzian force type fibre-optic magnetic sensor is reported attaining frequency-independent sensitivity in the range 1 Hz to 10 kHz with minimum detectable field down to 50 nT. It is also shown that this technique can introduce frequency superimposition, which enables measurement of AC magnetic fields at different points simultaneously with one interferometer     

Developmental expression and location of IGF-I and IGF-II mRNA and protein in skeletal muscle

To investigate the role of IGF in muscle development in vivo, developmental expression and location of IGF-I and -II protein and mRNA were examined in fetal, postnatal, and adult skeletal muscle. Muscle tissue was collected from 30-, 44-, 59-, 68-, 75-, 89-, and 109-d porcine fetuses, 21-d neonatal pigs, and 6-mo-old (adult) pigs. Relative amounts of IGF-II mRNA peaked (P < .05) in 59-d fetal muscle and decreased thereafter. Inversely, muscle IGF-I expression increased (P < .05) to maximal levels around birth. For in situ hybridization, frozen muscle tissue sections (10 microm) were hybridized with a hydrolyzed form of the same riboprobes or incubated with polyclonal or monoclonal antibodies to IGF-I or -II, respectively. The majority of IGF-I and IGF-II mRNA was localized to developing muscle fibers, whereas little signal was found in the surrounding connective tissues. Immunofluorescent localization of IGF-I and -II confirmed that muscle IGF are present in developing muscle fibers. Collectively, these data show that IGF-I and -II are expressed and produced primarily in muscle cells within developing muscle tissue and support the hypothesis that IGF-I and -II modulate fetal muscle development.     

Automatic optical loss compensation with erbium-doped fiberamplifier

The effect of unwanted optical loss varying over 15 dB is automatically offset with an erbium-doped fiber amplifier used in an optical feedback configuration. The loss compensation is possible for signal wavelengths over a 13 nm range centered at about 1550 nm. The system dynamic range for loss fluctuation frequencies is zero to several kilohertz. The proposed loss compensation scheme simultaneously provides an automatic gain control function that stabilizes the gain against slow changes in input signal power or pump power