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In the present study, magnesium composites are synthesised through the addition of nano-alumina and micrometre copper particulates in AZ31 magnesium alloy using the technique of disintegrated melt deposition. Nano-alumina and micrometre size copper particulates are known to significantly enhance the ductility and strength of magnesium materials respectively. The simultaneous addition of Cu and nano-Al2O3particulates led to an overall improvement in both microstructural characteristics in terms of distribution and morphology of intermetallics/particulates and mechanical response of AZ31. The 0·2 yield strength increased from 180 to 300 MPa (67), while the ductility increased by almost 24. The overall tensile properties assessed in terms of work of fracture improved by 66. An attempt is made to correlate the tensile response of composites with their microstructural characteristics. The results suggest that these alloy composites have significant potential in diverse and wider engineering applications when compared to AZ31 alloy.

New thin‐film dielectrics and nanolaminates have been synthesized via aqueous‐solution deposition of Hf and Zr sulfates, where facile gelation and vitrification of the precursor solution have been achieved without organic additives. X‐ray reflectivity, imaging, and metal‐insulator‐metal capacitor performance reveal that smooth, atomically dense films are readily produced by spin coating and modest thermal treatment (T< 325 °C). Dielectric characteristics include permittivities covering the range of 9–12 with breakdown fields up to 6 MV cm–1. Performance as gate dielectrics is demonstrated in field‐effect transistors exhibiting small gate‐leakage currents and qualitatively ideal device performance. The low‐temperature processing, uniformity, and pore‐free nature of the films have also allowed construction of unique, high‐resolution nanolaminates exhibiting individual layers as thin as 3 nm.

W/Al2O3 nanolaminates were fabricated using atomic layer deposition (ALD) techniques. ALD of tungsten was performed using alternating exposures of WF6 and Si2H6. ALD of Al2O3 was performed using alternating exposures of Al(CH3)3 and H2O. The fabrication of optimum nanolaminates was very dependent on nucleation during the ALD of each layer. The nucleation of Al2O3 ALD on W surfaces and W ALD on Al2O3 surfaces was examined using quartz crystal microbalance investigations. Al2O3 ALD on W nucleated easily during the first Al(CH3)3/H2O reaction cycle. In contrast, W ALD nucleation on Al2O3 required multiple WF6/Si2H6 reaction cycles and was very sensitive to the Si2H6 exposure. The W ALD nucleation required at least six or seven WF6/Si2H6 reaction cycles. The optimum reaction parameters for nucleation were utilized to fabricate W/Al2O3 nanolaminates with a total targeted thickness of ~1000 Å that were composed of various numbers of bilayers. Transmission electron microscopy (TEM) images revealed very well defined two-bilayer and four-bilayer W/Al2O3 nanolaminates grown at 177 °C. Depth-profile secondary ion mass spectrometry (SIMS) measurements confirmed the composition of the W/Al2O3 nanolaminates. Both the TEM and SIMS results showed that sharper interfaces were observed when W ALD nucleates on Al2O3, and rougher interfaces were observed when Al2O3 ALD nucleates on W. X-ray reflectivity (XRR) investigations indicated that the W/Al2O3 nanolaminates were much thicker than the ~1000 Å target for the total thickness when the W/Al2O3 nanolaminates were composed of a larger number of bilayers. These results were consistent with much lower than expected film densities for the thin Al2O3 ALD nanolayers. Atomic force microscope studies revealed that the surface roughness of W/Al2O3 nanolaminates was lower at lower growth temperatures and lower at higher interfacial densities. XRR investigations also revealed a pronounced Bragg peak with a high X-ray reflectivity from 64-bilayer W/Al2O3 nanolaminates grown at 177 °C. The X-ray reflectivity of the 64-bilayer W/Al2O3 nanolaminates grown at 177 °C was constant versus annealing up to 500 °C. The reflectivity then dropped rapidly for annealing at ≥600 °C. This thermal instability will place some limits on the application of W/Al2O3 nanolaminates as thermal barrier coatings and X-ray mirrors.

Slab and cluster models are used to study H2 desorption from a single dimer of the Si(100)−2 × 1 surface. The cluster models are constructed using geometries obtained from slab-model optimizations. The largest cluster model considered, Si89H62, contains eight surface dimers and gives reaction and activation energies for desorption nearly identical with the slab-model values when the same electronic structure method is used. The barrier for H2 desorption, calculated using the Si89H62 cluster model and the Becke3LYP functional, is 64.3 kcal/mol. When this result is corrected for the effects of basis set expansion and vibrational zero-point energy correction, the barrier decreases to about 61.0 kcal/mol, which is only 4.0 kcal/mol greater than the observed desorption barrier.

Insulin inhibits apolipoprotein B (apoB) secretion by primary rat hepatocytes through activation of phosphoinositide 3-kinase (PI 3-K). Current studies demonstrate that the PI 3-K inhibitor wortmannin inhibits both basal and insulin-stimulated PI 3-K activities. Wortmannin and LY 294002, two structurally distinct PI 3-K inhibitors, prevent insulin-dependent inhibition of apoB secretion in a dose-dependent manner. To link PI 3-K activation to insulin action on apoB, we investigated whether insulin induced localization of activated PI 3-K to the endoplasmic reticulum (ER), where apoB biogenesis is initiated. Insulin action results in a significant redistribution of PI 3-K to a low density microsome (LDM) fraction containing apoB protein and apoB mRNA. Insulin stimulates a significant increase in PI 3-K activity associated with insulin receptor substrate-1 as well as an increase in insulin receptor substrate-1/PI 3-K mass in LDM. Subfractionation of LDM on sucrose density gradients shows that insulin significantly increases the amount of PI 3-K present in an ER fraction containing apoB. Insulin stimulates PI 3-K activity in smooth and rough microsomes isolated from rat hepatocytes, the latter of which contain rough ER as demonstrated by electron microscopy. Studies indicate that 1) PI 3-K activity is necessary for insulin-dependent inhibition of apoB secretion by rat hepatocytes; 2) insulin action leads to the activation and localization of PI 3-K in an ER fraction containing apoB; and 3) insulin stimulates PI 3-K activity in the rough ER.

The effect of frequency-dependent advantage in wheat was investigated by growing F1. hybrid seeds of the crosses (Warimek X Halberd) and (Wariquam x Halberd) in a stand of Halberd at 5 frequencies: 4 %, 6.25 %, 11.11 %, 25 % and 50 %. A reduction of 35 % to 40 % in grain yield of individual plants was observed with both hybrids as their frequencies changed from 4% to 50 %. A similar trend with frequency was noted for several other plant characteristics, including total grain number, particularly with those measured towards the end of the growing season. Halberd plants did not show a corresponding increase as their frequency declined from 96 % to 50%. — The following season, 76 F4 lines from the cross (Warimek X Halberd) and 70 F4 lines from (Wariquam x Gabo) were grown at frequencies of 6.25% and 18.75% in machine sown stands of Wariquam and Halberd, respectively. Again grain yield decreased as genotypic frequency increased. Furthermore, there was a positive correlation between frequency-dependent advantage and relative grain yield, suggesting that high yielding genotypes show a greater advantage at low frequencies than lower yielding ones.

This case report describes twin sisters, one with rudimentary streak gonads and the other with normal ovarian function. Both siblings had normal 46,XX karyotypes, and zygosity testing indicated that they were identical twins. Discordance of identical twins for 46,XX pure gonadal dysgenesis suggests that environmental factors may be a causative factor in some of the karyotypically normal 46,XX forms of gonadal dysgenesis.

The effect of level of different counterion forms of $$N{H}_{4}^{+}$$ or $$N{O}_{3}^{-}$$ or both, on establishment of the Rhizobium trifolii-Trifolium repens symbiosis was evaluated in plants cultured under bacteriologically controlled conditions. Ammonium had little effect on nodule formation, and even after $$N{H}_{4}^{+}$$ exhaustion there was little compensatory nodule formation. Plant growth, nodule mass and acetylene reduction activity all declined with increasing levels of $$N{H}_{4}^{+}$$. Except for $$HC{O}_{3}^{-}$$, different $$N{H}_{4}^{+}$$ counterion forms had little effect on plant growth, nodule number and mass, and acetylene reduction activity. Ammonium markedly decreased pH, the extent being dependent upon $$N{H}_{4}^{+}$$ level and counterion present. Nitrate inhibited nodulation while levels remained in excess of plant uptake. Compensatory nodulation followed exhaustion of $$N{H}_{4}^{+}$$ or $$N{O}_{3}^{-}$$ at lower $$N{H}_{4}^{+}$$ or $$N{O}_{3}^{-}$$ levels. Nodule mass and acetylene reduction activity decreased, but plant growth increased with increasing $$N{H}_{4}^{+}$$ or $$N{O}_{3}^{-}$$ levels. Nitrate raised the pH of the nutrient solution by one unit or less. Different $$N{H}_{4}^{+}$$ or $$N{O}_{3}^{-}$$ counterion forms had little effect on the symbiosis or plant growth. Ammonium nitrate severely inhibited nodulation but on exhaustion marked compensatory nodulation occurred. The patterns of nodule mass, acetylene reduction activity and plant growth with increasing NH4NO3 levels were similar to $$N{H}_{4}^{+}$$ or $$N{O}_{3}^{-}$$ alone. Plants provided with NH4NO3 or no nitrogen were similar in only slightly decreasing pH.

In studies of Trifolium repens nitrogen nutrition, the control of nutrient solution pH using dipolar buffers, was evaluated in tube culture under sterile conditions. Five buffers; MES, ADA, ACES, BES and MOPS with pK2s (20 °C) of 6.15, 6.60, 6.90, 7.15 and 7.20 respectively, at a concentration of 2.0 mol m−3, were provided to inoculated Trifolium repens growing in nutrient solution containing 7.13 mol m−3 nitrogen as (NH4)2SO4. Initial pH of each solution was adjusted to the appropriate buffer pK2 Two buffers, ADA and ACES completely inhibited plant growth. The remaining buffers had little effect in limiting pH change, although plant dry matter was higher and nodule numbers lower in the presence of these buffers. MES and MOPS were supplied to nutrient solutions with and without 7.13 mol m−3 (NH4)2SO4, at concentrations ranging from 0–12 mol m−3. MES at 9 mol m−3 and 12 mol m−3 reduced growth of plants reliant on the symbiosis for providing nitrogen. The provision of MES to plants provided with NH4+ significantly increased plant yield and reduced nodule number at all concentrations. MOPS did not affect plant yield or nodule number. The use of dipolar buffers in legume nitrogen nutrition studies is considered in terms of buffering capacity, and the side effects on plant growth and symbiotic development.