124 research outputs found
Nanoscale electrical conductivity imaging using a nitrogen-vacancy center in diamond
The electrical conductivity of a material can feature subtle, nontrivial, and
spatially-varying signatures with critical insight into the material's
underlying physics. Here we demonstrate a conductivity imaging technique based
on the atom-sized nitrogen-vacancy (NV) defect in diamond that offers local,
quantitative, and noninvasive conductivity imaging with nanoscale spatial
resolution. We monitor the spin relaxation rate of a single NV center in a
scanning probe geometry to quantitatively image the magnetic fluctuations
produced by thermal electron motion in nanopatterned metallic conductors. We
achieve 40-nm scale spatial resolution of the conductivity and realize a
25-fold increase in imaging speed by implementing spin-to-charge conversion
readout of a shallow NV center. NV-based conductivity imaging can probe
condensed-matter systems in a new regime, and as a model example, we project
readily achievable imaging of nanoscale phase separation in complex oxides.Comment: Supplementary information at en
Lukutaito ja kestÀvÀ kehitys
The author deals with the topic of sustainable development and literacy from the viewpoint of a poor developing country. The president of the Sarvodaya Movement, which represents a new literacy and development strategy, presents us with a new literacy of enlightenment as an alternative to the traditional! and functional concept of literacy. The author considers it to be considerably more appropriate for the needs of the exploited and discriminated against sectors of society as they strive to improve their lot.Kirjoittajan aiheena on kestÀvÀn kehityksen kÀsite ja lukutaito köyhÀn kehitysmaan nÀkökulmasta. Uudenlaista lukutaito- ja kehitysstrategiaa edustavan Sarvodaya-liikkeen presidentti tuo traditionaalisen ja funktionaalisen lukutaitokÀsitteen rinnalle uuden, enlightenment literacyn, jonka kirjoittaja katsoo sopivan verrattomasti paremmin sorrettujen ja syrjittyjen kansankerrosten pyrkimyksiin parantaa asemaansa
Institutions, impact synergies and food security: a methodology with results from the Kala Oya Basin, Sri Lanka
Institutional development / Development plans / Development policy / Impact assessment / River basins / Food security / Models
Applicability of frozen-viscosity models of unsteady wall shear stress
The validity of assumed frozen-viscosity conditions underpinning an important class of theoretical models of unsteady wall shear
stress in transient flows in pipes and channels is assessed using detailed computational fluid dynamics (CFD) simulations. The need for
approximate one-dimensional Ă°1DĂfx; tg models of the wall stress is unavoidable in analyses of transient flows in extensive pipe networks
because it would be economically impracticable to use higher order methods of analysis. However, the bases of the various models have never
been established rigorously. It is shown herein that a commonly used approach developed by the first authors is flawed in the case of smoothwall
flows although it is more plausible for rough-wall flows. The assessment process is undertaken for a particular, but important, unsteady
flow case, namely, a uniform acceleration from an initially steady turbulent flow. First, detailed predictions from a validated CFD method are
used to derive baseline solutions with which predictions based on approximate models can be compared. Then, alternative solutions are
obtained using various prescribed frozen-viscosity distributions. Differences between these solutions and the baseline solutions are used
to determine which frozen-viscosity distributions are the most promising starting points for developing 1Dfx; tg models of unsteady components
of wall shear stress. It is shown that no frozen-viscosity distribution performs well for large times after the commencement of an
acceleration. However, even the simplest approximation (laminar) performs well for short durationsâwhich is when the greatest amplitudes
of the unsteady components occu
Unsteady skin friction experimentation in a large diameter pipe
Experimental data for the validation of theoretical models of unsteady skin friction are limited and are available only for a few low Reynolds number flow cases. There is a strong need for detailed measurements in flows at high Reynolds numbers. In addition, there is a need for a wider range of well-controlled acceleration/deceleration rates and detailed visualization of flow structure and profiles. To address these needs, a large-scale pipeline apparatus at Deltares, Delft, The Netherlands, has been used for unsteady skin friction experiments including acceleration, deceleration and acoustic resonance tests. The apparatus consists of a constant head tank, a horizontal 200 mm diameter pipe of changeable length (44 to 49 metres) and a control valve at the downstream end. In addition to standard instrumentation, two distinctive instruments have been used: hot-film wall shear stress sensors ("direct" measurement of wall shear stress) and a PIV set-up for measurement of unsteady flow profiles. This paper describes the test rig, the instrumentation layout and the test programme. Finally, some initial test results are presented and discussed
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Impact assessment and adaptation to climate change of plantations in Sri Lanka
This report documents the work undertaken by the IRI, FECT, NRMS and University of
Peradeniya as part of the overall project. Separate reports were prepared by the Tea
Research Institute, Coconut Research Institute and the Department of Meteorology in Sri
Lanka. The work at IRI, FECT and NRMS has proceeded satisfactorily. The work was in
the domain of climate and climate change, crop-climate impact analysis and contributions
to synthesis. We have contributed significantly in terms of research output and in
capacity building, which were the goals of the AIACC project
Frequency of natural out-crossing in partially cleistogamous pigeonpea lines in diverse environments
Natural out-crossing is the major cause of loss of varietal purity in pegeonpea [Cajanus cajan (L.) Millsp.]. The frequency of natural out-crossing of partially cleistogamous mutant lines, characterized by a modified keel and filamentous anthers, was studied at two locations in Sri Lanka and three locations in India. Indeterminate growth habit and normal floral morphology were used as dominant markers and the frequency of anural out-crossing was estimated as percentage of the observed hybrid plants. Natural out-crossing in the mutant lines in Sri Lanka ranged from 0.14 to 1.33% in comparison to 6.34 to 19.64% in the controls. In the Indian environments, natural outcrossing ranged from 0.16 to 2.67%. The mutant was higly stable over diverse environments, and may be of considerable economic importance in pigeonpea improvement and seed-production programs
Dynamics of notch pathway expression during mouse testis post-natal development and along the spermatogenic cycle
Articles in International JournalsThe transcription and expression patterns of Notch pathway components (Notch 1â3, Delta1 and 4, Jagged1) and effectors
(Hes1, Hes2, Hes5 and Nrarp) were evaluated (through RT-PCR and IHC) in the mouse testis at key moments of post-natal
development, and along the adult spermatogenic cycle. Notch pathway components and effectors are transcribed in the
testis and expressed in germ, Sertoli and Leydig cells, and each Notch component shows a specific cell-type and timewindow
expression pattern. This expression at key testis developmental events prompt for a role of Notch signaling in prepubertal
spermatogonia quiescence, onset of spermatogenesis, and regulation of the spermatogenic cycle
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