Microscale application of column theory for high resolution force and displacement sensing

We present the design, fabrication and experimental validation of a novel device that exploits the amplification of displacement and attenuation of structural stiffness in the post-buckling deformation of slender columns to obtain pico-Newton force and nanometer displacement resolution even under an optical microscope. The extremely small size, purely mechanical sensing scheme and vacuum compatibility of the instrument makes it compatible with existing visualization tools of nanotechnology. The instrument has a wide variety of potential applications ranging from electro-mechanical characterization of one dimensional solids to single biological cells

Fish seed production in ricefields: participatory training and extension manual

Seed (aquaculture), Rice field aquaculture, Rice fields, Manuals Oreochromis niloticus

Effect of tillage and residue retention on maize productivity

In Bangladesh, maize is generally sown after extensive tilth and minimum residue retention. Conservation agriculture (CA) systems reduce the input costs, machinery use, CO2 emissions; and improve soil health (Raper et al., 1994). Crop residues are known to affect soil physical properties (Hulugalle et al., 1986), availability of nutrients (Wade and Sanchez, 1983; Asghar et al., 2006) and soil biological activity (Tian et al., 1993). Crop residue retention has been suggested to improve overall soil fertility and to support sustainable crop production. Crop residue retention under no tillage system reduce soil erosion, increase soil organic matter (SOM), and reduce requirement of labour and fuel under cereal grain and row crop culture (Salinas-Garcia et al., 1997). Kumar and Goh (2000) reported that incorporation of crop residues is essential for sustaining soil productivity through replenishing SOM that not only a key indicator of soil quality, but it also supplies essential nutrients upon mineralization (N, P, and S) and improves soil physical, chemical, and biological properties (Kumar et al., 2001). In our country, the crop residue is used mostly for cattle feed (Saadullah et al., 1991), fuel for stove and some cases burning. It is essential to estimate the amount of crop residue that should be retained in field to get the benefits. Therefore, the present research investigated to find out the minimum tillage with residue retention could be an effective element for maize production

Optimal protocols for quantum quenches of finite duration in the Luttinger model

Reaching a target quantum state from an initial state within a finite temporal window is a challenging problem due to nonadiabaticity. We study the optimal protocol for switching on interactions to reach the ground state of a weakly interacting Luttinger liquid within a finite time tau, starting from the noninteracting ground state. The protocol is optimized by minimizing the excess energy at the end of the quench, or by maximizing the overlap with the interacting ground state. We find that the optimal protocol is symmetric with respect to tau/2, and can be expressed as a functional of the occupation numbers of the bosonic modes in the final state. For short quench durations, the optimal protocol exhibits fast oscillation and excites high-energy modes. In the limit of large tau, minimizing energy requires a smooth protocol while maximizing overlap requires a linear quench protocol. In this limit, the minimal energy and maximal overlap are both universal functions of the system size and the duration of the protocol

Deformation of a Trapped Fermi Gas with Unequal Spin Populations

The real-space densities of a polarized strongly-interacting two-component Fermi gas of $^6$Li atoms reveal two low temperature regimes, both with a fully-paired core. At the lowest temperatures, the unpolarized core deforms with increasing polarization. Sharp boundaries between the core and the excess unpaired atoms are consistent with a phase separation driven by a first-order phase transition. In contrast, at higher temperatures the core does not deform but remains unpolarized up to a critical polarization. The boundaries are not sharp in this case, indicating a partially-polarized shell between the core and the unpaired atoms. The temperature dependence is consistent with a tricritical point in the phase diagram.Comment: Accepted for publication in Physical Review Letter

Analysis of a fully packed loop model arising in a magnetic Coulomb phase

The Coulomb phase of spin ice, and indeed the Ic phase of water ice, naturally realise a fully-packed two-colour loop model in three dimensions. We present a detailed analysis of the statistics of these loops, which avoid themselves and other loops of the same colour, and contrast their behaviour to an analogous two-dimensional model. The properties of another extended degree of freedom are also addressed, flux lines of the emergent gauge field of the Coulomb phase, which appear as "Dirac strings" in spin ice. We mention implications of these results for related models, and experiments.Comment: 5 pages, 4 figure