Electromagnetic response of LaO_0.94F_0.06FeAs: AC susceptibility and microwave surface resistance

We discuss on the electromagnetic response of a polycrystalline sample of LaO_0.94F_0.06FeAs exposed to DC magnetic fields up to 10 kOe. The low- and high-frequency responses have been investigated by measuring the AC susceptibility at 100 kHz and the microwave surface resistance at 9.6 GHz. At low as well as high DC magnetic fields, the susceptibility strongly depends on the amplitude of the AC driving field, highlighting enhanced nonlinear effects. The field dependence of the AC susceptibility exhibits a magnetic hysteresis that can be justified considering the intragrain-field-penetration effects on the intergrain critical current density. The microwave surface resistance exhibits a clockwise magnetic hysteresis, which cannot be justified in the framework of the critical-state models of the Abrikosov-fluxon lattice; it may have the same origin as that detected in the susceptibility.Comment: 8 pages, 4 embedded eps figures; Proceedings of the 9th EUCAS Conference (Dresden, Germany, September 13-17, 2009

Effect of orthophosphate on the transaldolase reaction.

In previous studies' with a dialyzed supernatant fraction from rat liver it was observed that the formation of heptulose phosphate from fructose g-phosphate was significantly inhibited by inorganic phosphate. It has since been shown (1, 2) that the activity of the dialyzed liver fraction can be related to its content of transketolase and transaldolase and it became of interest to determine whether the inhibition of the over-all process by phosphate was due to its effect on one or both of the enzymes involved in this process. Preliminary experiments indicated that both transketolase and transaldolase were inhibited by inorganic phosphate when the enzymes were tested in the usual assay procedures. The effect of phosphate on transaldolase is reported in the present paper

Microwave Harmonic Emission in MgB2 Superconductor: Comparison with YBaCuO

We report results of microwave second-harmonic generation in ceramic samples of MgB2, prepared by different methods. The SH signal has been investigated as a function of the temperature and the static magnetic field. The results are discussed in the framework of models reported in the literature. We show that the peculiarities of the SH signal are related to the specific properties of the sample. A comparison with the results obtained in ceramic and crystalline YBa(2)Cu(3)O(7) shows that the second-harmonic emission in MgB2 is weaker than that observed in ceramic YBa(2)Cu(3)O(7).Comment: 13 pages, 6 figures; Proceedings of Third Workshop on Metamaterials and Special Materials for Electromagnetic Applications and TLC (Rome, 30-31 March, 2006

Microwave response of bulk MgB2 samples of different granularity

The microwave response of three high-density bulk MgB2 samples has been investigated in the linear and nonlinear regimes. The three samples, characterized by different mean size of grains, have been obtained by reactive infiltration of liquid Mg in powdered B preforms. The linear response has been studied by measuring the microwave surface impedance; the nonlinear response by detecting the power radiated by the sample at the second-harmonic frequency of the driving field. Our results suggest that bulk MgB2 prepared by the liquid Mg infiltration technique is particularly promising for manufacturing resonant cavities operating at microwave frequencies.Comment: 4 pages, 2 embedded figures; Proceedings of 7th EUCAS Conference (11-15 September 2005, Vienna - Austria

CLEAVAGE OF SEDOHEPTULOSE 1,7-DIPHOSPHATE BY A PURIFIED RAT LIVER DIPHOSPHATASE.

SUMMARY treatment. A simple procedure is described for the purification, from rat None of a variety of other monophosphate and diphosphate liver, of a diphosphatase activity which cleaves both fructose esters tested as substrates was cleaved by the purified enzyme diphosphate and sedoheptulose diphosphate to fructose 6-phos- at significant rates. These results suggest an absolute require- phate and sedoheptulose 7-phosphate, respectively. ment for the presence of two phosphate groups and also for the Evidence that a single enzyme is responsible for both reactions configuration found in FDP and SDP. n-Bibulose 1,5-diphos- is derived from the results of the purification steps, from kinetic phate differs in the configuration at C-3 and is not attacked. measurements, and from other properties. The enzyme has no With respect to the physiological role of the diphosphatase, activity with a variety of monophosphate esters and other di- although it has been generally recognized that fructose diphos- phosphate esters. phatase may represent a key enzyme in the synthesis of glycogen Both activities are present in the liver of all mammalian species from 3 carbon fragments, no direct evidence for a role of sedo- studied. heptulose diphosphatase has yet been obtained. REFERENCES Three possibilities may be considered with respect to the physiological significance of the latter activity. (a) It may be 1. GOMORI, G., J

Endurance training damages small airway epithelium in mice.

RATIONALE: In athletes, airway inflammatory cells were found to be increased in induced sputum or bronchial biopsies. Most data were obtained after exposure to cold and dry air at rest or during exercise. Whether training affects epithelial and inflammatory cells in small airways is unknown. OBJECTIVES: To test whether endurance training under standard environmental conditions causes epithelial damage and inflammation in the small airways of mice. METHODS AND MEASUREMENTS: Formalin-fixed, paraffin-embedded lung sections were obtained in sedentary (n = 14) and endurance-trained (n = 16) Swiss mice at baseline and after 15, 30, and 45 days of training. The following variables were assessed (morphometry and immunohistochemistry) in small airways (basement membrane length < 1 mm): (1) integrity, proliferation, and apoptosis of bronchiolar epithelium; and (2) infiltration, activation, and apoptosis of inflammatory cells. MAIN RESULTS: Compared with sedentary mice, bronchiolar epithelium of trained mice showed progressive loss of ciliated cells, slightly increased thickness, unchanged goblet cell number and appearance, and increased apoptosis and proliferation (proliferating cell nuclear antigen) (p < 0.001 for all variables). Leukocytes (CD45(+) cells) infiltrated airway walls (p < 0.0001) and accumulated within the lumen (p < 0.001); however, apoptosis of CD45(+) cells did not differ between trained and sedentary mice. Nuclear factor-kappaB translocation and inhibitor-alpha of NF-kappaB (IkappaBalpha) phosphorylation were not increased in trained compared with sedentary mice. CONCLUSIONS: Bronchiolar epithelium showed damage and repair associated with endurance training. Training increased inflammatory cells in small airways, but inflammatory activation was not increased. These changes may represent an adaptive response to increased ventilation during exercise

Superconducting Microwave Cavity Made of Bulk MgB2

We report the successful manufacture and characterization of a microwave resonant cylindrical cavity made of bulk MgB2 superconductor (Tc = 38.5 K), which has been produced by the Reactive Liquid Mg Infiltration technique. The quality factor of the cavity for the TE011 mode, resonating at 9.79 GHz, has been measured as a function of the temperature. At T = 4.2 K, the unloaded quality factor is 2.2x10^5; it remains of the order of 10^5 up to T ~ 30 K. We discuss the potential performance improvements of microwave cavities built from bulk MgB2 materials produced by reactive liquid Mg infiltration.Comment: 7 pages, 2 embedded figures, accepted for publication in Supercond. Sci. Techno