9,961 research outputs found
GM crops and gender issues
Correspondence in the December issue by Jonathan Gressel not only states that gender issues in rural settings have not been adequately addressed with respect to weed control biotech but also asserts that such technology can increase the quality of life of rural women in developing countries. Improved weed control is a labor-saving technology that can result in less employment in a labor surplus rural economy. Often in rural areas, wage income is the main source of income and an important determinant of the quality of life, particularly where employment opportunities are generally limited. Apart from soil preparation, planting and weeding, harvesting is also 'femanual' work that can generate more employment if yields are higher. Biotech can enhance the quality of life of women but only if the technology is associated with overall generation of rural employment
A Unified treatment of small and large- scale dynamos in helical turbulence
Helical turbulence is thought to provide the key to the generation of
large-scale magnetic fields. Turbulence also generically leads to rapidly
growing small-scale magnetic fields correlated on the turbulence scales. These
two processes are usually studied separately. We give here a unified treatment
of both processes, in the case of random fields, incorporating also a simple
model non-linear drift. In the process we uncover an interesting plausible
saturated state of the small-scale dynamo and a novel analogy between quantum
mechanical (QM) tunneling and the generation of large scale fields. The steady
state problem of the combined small/large scale dynamo, is mapped to a
zero-energy, QM potential problem; but a potential which, for non-zero mean
helicity, allows tunneling of bound states. A field generated by the
small-scale dynamo, can 'tunnel' to produce large-scale correlations, which in
steady state, correspond to a force-free 'mean' field.Comment: 4 pages, 1 figure, Physical Review Letters, in pres
Further constraints on electron acceleration in solar noise storms
We reexamine the energetics of nonthermal electron acceleration in solar
noise storms. A new result is obtained for the minimum nonthermal electron
number density required to produce a Langmuir wave population of sufficient
intensity to power the noise storm emission. We combine this constraint with
the stochastic electron acceleration formalism developed by Subramanian &
Becker (2005) to derive a rigorous estimate for the efficiency of the overall
noise storm emission process, beginning with nonthermal electron acceleration
and culminating in the observed radiation. We also calculate separate
efficiencies for the electron acceleration -- Langmuir wave generation stage
and the Langmuir wave -- noise storm production stage. In addition, we obtain a
new theoretical estimate for the energy density of the Langmuir waves in noise
storm continuum sources.Comment: Accepted for publication in Solar Physic
Implementation of security module to protect programme theft in microcontroller-based applications
Source code plagiarism has become a serious threat for the development of small scale embedded industries and also the violations of intellectual property right are a threat for the development of hardware system. There are many software solutions for comparing source codes, but they are often not realistic in the present scenario. Digital watermarking scheme is one of the possible solutions for this problem. A novel watermarking technique is employed so that it can be easily and reliably detected by special techniques. In this paper, verification methods are presented to detect software plagiarism in the embedded application software without the implemented source code. All the approaches use side-channel information obtained during the execution of the suspicious code. The primary method is passive, i.e. no previous modification of the original code is required. It determines that the Hamming weights of the executed instructions of the suspicious device are used and uses string matching algorithms for comparisons with a reference implementation. The other method inserts additional code fragments as a watermark that can be identified in the power consumption of the executed source code. Proposed approaches are robust against code-transformation attacks
Ion viscosity mediated by tangled magnetic fields: an application to black hole accretion disks
We derive expressions for a ``hybrid'' viscosity arising from Coulomb collisions between ions in the presence of tangled magnetic fields. Such magnetic fields are expected to be embedded in accretion flows onto black holes and other compact objects. Ion viscosity in the absence of magnetic fields has been shown to appreciable in hot accretion disks, but it was thought that the presence of the smallest of magnetic fields would effectively quench it. We show that the hybrid viscosity in hot (ion temperatures around 10^11-10^12 K) accretion disks results in values of the Shakura Sunyaev \alpha parameter around 0.01 to 0.1-0.5. We do not model the generation of the tangled magnetic fields; we merely assume its presence and assume it to be arbitrarily strong
- …