Towards a more situation appropriate and responsive extension approach for Ethiopia

This paper investigates the influence of some selected personal, environmental and intervening factors on the adoption behaviour of dairy producers with the object of identifying the most important causes of behaviour and thus finding a more purposeful and effective way of changing the adoption behaviour. 200 farmers were randomly drawn form a total of about 430 standing members of Ada Liben Woreda Dairy And Dairy Products Marketing Association (ALWDADPMA) in Debrezeit, Ethiopia. In the analysis of data the ordinary least squares (OLS) regression methods were employed to identify the most important determinants associated with behavioural change The results indicate that, in general, the intervening variables tend to have the highest prediction value. They were found to explain 68.3 percent and 80.9 percent of the variance of behaviour associated with the practice adoption and production efficiency, while the independent variables explained only 17.8 percent and 19.3 percent of the variation, respectively. The contribution of independent variables appears substantial only when their indirect effect (effect through intervening variables) is considered. SA Jnl. Agric. Ext. Vol 33 2004: 52-6

Access to metastable complex ion conductors via mechanosynthesis: Preparation, microstructure and conductivity of (Ba,Sr)LiF3 with inverse perovskite structure

Highly metastable Ba1−xSrxLiF3 (0 < x ≤ xmax ≈ 0.4) with an inverse perovskite structure analogous to that of BaLiF3 was synthesized by soft mechanical treatment of BaF2 and LiF together with SrF2 at ambient temperature. Ex as well as in situX-ray powder diffraction (XRPD) measurements show that heat treatment at 393 K initiates the decomposition of the mixed phase into BaLiF3, LiF and (Sr,Ba)F2. Structural details of the metastable compound (Ba,Sr)LiF3 were investigated by ultrafast 19F magic angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy. Interestingly, five magnetically inequivalent F sites were identified which correspond to fluorine anions coordinated by a variable number of Ba and Sr cations, respectively. Details from XRPD and NMR spectroscopy are discussed with respect to the formation mechanisms and thermal stability of the as prepared fluorides. Impedance spectroscopy is used to characterize (long-range) ionic transport properties. Results are compared with those obtained recently on mechanosynthesized BaLiF3

Formation and Elimination of Anti-site Defects during Crystallization in Perovskite Ba1–xSrxLiF3

The defect density of a material is decisive for its physical, chemical and mechanical properties. Accordingly, defect tuning is desirable for applications spanning, e.g., batteries, fuel cells, electronics, optics, catalysis and mechanical strength and resilience. Here we simulate the mechanochemical synthesis of the perovskite Ba1-xSrxLiF3 by compressing a BaLiF3 nanoparticle with a SrLiF3 nanoparticle under conditions likely to occur during high-energy ball milling. We investigate the crystallization process and the ionic mobility of the system and compare with experiment. Animations of the crystallization, simulated under high pressure, revealed that cations, within the crystallization front, would commonly condense onto ‘incorrect’ lattice sites, in some cases eventually leading to the formation of anti-site defects. However, most of these cations would then re-amorphise and the ‘correct’ cation would take its place – rectifying the defect. Crucially, it is the amorphous/crystalline interface that enables such repair because the ions are mobile in this region. The simulations reveal high ion mobility close to the anti-site defects and other defective regions, but no ion mobility in the defect free regions of BaLiF3. The MD simulations indicate that high-energy ball milling might reduce the anti-site defect density in a material by exposing these defects to the surface or creating amorphous regions within the crystallite which then would allow localized recrystallization, enabling defect repair. This assumption is a possible explanation for the reduced ion mobility, revealed by NMR spectroscopy, and, thus, most likely smaller defect density in BaLiF3 prepared by high-energy ball milling compared to thermally synthesized BaLiF3¬ samples

A case study for the formation of stanene on a metal surface

The discovery and realization of graphene as an ideal two-dimensional (2D) material has triggered extensive efforts to create similar 2D materials with exciting spin-dependent properties. Here, we report on a novel Sn 2D superstructure on Au(111) that shows similarities and differences to the expected electronic features of ideal stanene. Using spin- and angle-resolved photoemission spectroscopy, we find that a particular Sn/Au superstructure reveals a linearly dispersing band centered at the Γ-point and below the Fermi level with antiparallel spin polarization and a Fermi velocity of vF ≈ 1×106 m/s, the same value as for graphene. We attribute the origin of the band structure to the hybridization between the Sn and the Au orbitals at the 2D Sn-Au interface. Considering that free-standing stanene simply cannot exist, our investigated structure is an important step towards the search of useful stanene-like overstructures for future technological applications

A simple and straightforward mechanochemical synthesis of the far-from-equilibrium zinc aluminate, ZnAl₂O₄, and its response to thermal treatment

Zinc aluminate (ZnAl2O4) nanoparticles with an average size of about 10 nm are synthesized via one-step mechanochemical processing of the ZnO : g-Al2O3 stoichiometric mixture at ambient temperature. The mechanochemically induced formation of the phase is followed by XRD and 27Al MAS NMR. Highresolution TEM studies reveal a non-uniform nanostructure of mechanosynthesized aluminate consisting of ordered grains surrounded or separated by disordered surface and interfacial regions. Due to the capability of 27Al MAS NMR to probe the local environment of the Al cations, valuable insights into the short-range structure of ZnAl2O4 on the °Angstr¨om length scale are provided. It is demonstrated that the as-prepared aluminate possesses a partly inverse spinel structure with a far-from equilibrium arrangement of cations and distorted polyhedra, which are spatially confined to the surface and interfacial regions with a volume fraction of ca. 50% and a thickness of ca. 1 nm. The response of the nanostructured ZnAl2O4 to subsequent thermal treatment is further investigated. It turned out that the thermally induced grain growth is accompanied by a release of microstrain, by a shrinkage of the lattice parameter, as well as by a variation in the oxygen parameter and metal–oxygen bond lengths. Evidence is given of the thermally induced redistribution of cations approaching their equilibrium positions. Upon heating above 1100 K, mechanosynthesized ZnAl2O4 relaxes towards a structural state that is similar to the bulk one

A Unique Mechanochemical Redox Reaction Yielding Nanostructured Double Perovskite Sr2_{2}FeMoO6_{6} With an Extraordinarily High Degree of Anti-Site Disorder

Strontium ferromolybdate, Sr(2)FeMoO(6), is an important member of the family of double perovskites with the possible technological applications in the field of spintronics and solid oxide fuel cells. Its preparation via a multi-step ceramic route or various wet chemistry-based routes is notoriously difficult. The present work demonstrates that Sr(2)FeMoO(6) can be mechanosynthesized at ambient temperature in air directly from its precursors (SrO, α-Fe, MoO(3)) in the form of nanostructured powders, without the need for solvents and/or calcination under controlled oxygen fugacity. The mechanically induced evolution of the Sr(2)FeMoO(6) phase and the far-from-equilibrium structural state of the reaction product are systematically monitored with XRD and a variety of spectroscopic techniques including Raman spectroscopy, (57)Fe Mössbauer spectroscopy, and X-ray photoelectron spectroscopy. The unique extensive oxidation of iron species (Fe(0) → Fe(3+)) with simultaneous reduction of Mo cations (Mo(6+) → Mo(5+)), occuring during the mechanosynthesis of Sr(2)FeMoO(6), is attributed to the mechanically triggered formation of tiny metallic iron nanoparticles in superparamagnetic state with a large reaction surface and a high oxidation affinity, whose steady presence in the reaction mixture of the milled educts initiates/promotes the swift redox reaction. High-resolution transmission electron microscopy observations reveal that the mechanosynthesized Sr(2)FeMoO(6), even after its moderate thermal treatment at 923 K for 30 min in air, exhibits the nanostructured nature with the average particle size of 21(4) nm. At the short-range scale, the nanostructure of the as-prepared Sr(2)FeMoO(6) is characterized by both, the strongly distorted geometry of the constituent FeO(6) octahedra and the extraordinarily high degree of anti-site disorder. The degree of anti-site disorder ASD = 0.5, derived independently from the present experimental XRD, Mössbauer, and SQUID magnetization data, corresponds to the completely random distribution of Fe(3+) and Mo(5+) cations over the sites of octahedral coordination provided by the double perovskite structure. Moreover, the fully anti-site disordered Sr(2)FeMoO(6) nanoparticles exhibit superparamagnetism with the blocking temperature T (B) = 240 K and the deteriorated effective magnetic moment μ = 0.055 μ (B) per formula unit

Hunger Artists: Yeast Adapted to Carbon Limitation Show Trade-Offs under Carbon Sufficiency

As organisms adaptively evolve to a new environment, selection results in the improvement of certain traits, bringing about an increase in fitness. Trade-offs may result from this process if function in other traits is reduced in alternative environments either by the adaptive mutations themselves or by the accumulation of neutral mutations elsewhere in the genome. Though the cost of adaptation has long been a fundamental premise in evolutionary biology, the existence of and molecular basis for trade-offs in alternative environments are not well-established. Here, we show that yeast evolved under aerobic glucose limitation show surprisingly few trade-offs when cultured in other carbon-limited environments, under either aerobic or anaerobic conditions. However, while adaptive clones consistently outperform their common ancestor under carbon limiting conditions, in some cases they perform less well than their ancestor in aerobic, carbon-rich environments, indicating that trade-offs can appear when resources are non-limiting. To more deeply understand how adaptation to one condition affects performance in others, we determined steady-state transcript abundance of adaptive clones grown under diverse conditions and performed whole-genome sequencing to identify mutations that distinguish them from one another and from their common ancestor. We identified mutations in genes involved in glucose sensing, signaling, and transport, which, when considered in the context of the expression data, help explain their adaptation to carbon poor environments. However, different sets of mutations in each independently evolved clone indicate that multiple mutational paths lead to the adaptive phenotype. We conclude that yeasts that evolve high fitness under one resource-limiting condition also become more fit under other resource-limiting conditions, but may pay a fitness cost when those same resources are abundant

The cytotoxic T cell proteome and its shaping by the kinase mTOR

High-resolution mass spectrometry maps the cytotoxic T lymphocyte (CTL) proteome and the impact of mammalian target of rapamycin complex 1 (mTORC1) on CTLs. The CTL proteome was dominated by metabolic regulators and granzymes and mTORC1 selectively repressed and promoted expression of subset of CTL proteins (~10%). These included key CTL effector molecules, signaling proteins and a subset of metabolic enzymes. Proteomic data highlighted the potential for mTORC1 negative control of phosphatidylinositol (3,4,5)-trisphosphate (PtdIns(3,4,5)P(3)) production in CTL. mTORC1 was shown to repress PtdIns(3,4,5)P(3) production and to determine the mTORC2 requirement for activation of the kinase Akt. Unbiased proteomic analysis thus provides a comprehensive understanding of CTL identity and mTORC1 control of CTL function