434 research outputs found
Design of a Broadband Amplifier for High Speed Applications
This paper provides comprehensive insight into the design approach followed for an amplifier dedicated to high speed base band signals. To demonstrate the methodology, an amplifier consisting of nine PHEMT cascode cells within a distributed amplifier topology was designed. The resulting frequency response is 40 GHz at the 3-dB point, and the output voltage for a 43 Gbps eye diagram is 7.3 Vpp at the chip terminal
Radon/helium studies for earthquake prediction in N-W Himalaya
The great Himalayan orogenic belt is one of the most active
intra-continental regions in the world where a dozen earthquakes exceeding 7.5M occurred in the past from 1897 through 1950. Radon monitoring started in the Kangra valley, Himachal Pradesh in 1989 under the Himalayan Seismicity Programme of the Goverment of India. Six stations were set up along the main boundary fault (MBF) of N-W Himalaya. Radon monitoring is carried out using three techniques, viz., track etch technique, emanometry and alpha-logger system in both soil-gas and groundwater. Radon anomalies are correlated with microseismic activity in the N-W Himalaya. The correlation index varies for different stations and there is no one-to-one correspondence between radon anomalies and seismic events. The Uttarkashi (Ms47.0) and Chamba earthquakes (Ms45.1) are postdicted using radon anomalies which occurred in soil-gas and groundwater, simultaneously. Currently, we are using multisensor probes for monitoring of radon and meteorological parameters simultaneously in the study area. Helium is being monitored along with radon at Palampur in soil-gas and in thermal springs in the Kullu and Parbati valleys of Himachal Pradesh. The He/Rn ratio will be used as a predictive tool for earthquakes
Are nonwoven synthetic pollination bags a better choice for sorghum breeding?
This work investigated the effects of seven pollination bag treatments on three varieties of sorghum for: grain loss to birds; total weight of five panicles (g); total grain weight of five panicles (g); average grain weight per panicle (g); germination per cent; and occurrence of grain mold during 2016. Varieties were: 1167048 hybrid (brown seeded); BR007B (red seeded); and P9401 (white seeded). The bag treatments were: 1. No bagging; 2. Kraft paper; 3. Kraft paper + plastic bag screen; 4 Used duraweb® SG1; 5. Used duraweb® SG2; 6. New duraweb® SG1; 7. New duraweld® SG2. High bird pressure resulted in 100% seed loss on uncovered panicles and 75% under Kraft paper pollination bags. Birds preferred white seeded P9401, which led to no seed recovery under Kraft paper bags. There was virtually no bird damage with all other pollination bags. For panicle and grain yields the varieties performed in the order 1167048>BR007B>P9401. Unprotected panicles and paper bag treatments had the lowest yields. Panicles covered with the new synthetic bags exhibited 195 to 652% higher yields compared to Kraft paper bags. Varieties x bag type interactions were not important as they contributed 4 to 6% to the total sum of squares for yield traits. Germination test under normal and stress conditions showed no significant adverse effect of bag treatments on seed health. Reused bags performed as well as new bags for all of these traits. Varieties differed significantly for the occurrence of five grain mold pathogens, with highest occurrence of Alternaria, up to 40%, on 1167048 hybrid. Of the five pathogens, bag types differed significantly for Phoma with the highest occurrence of 9% on re-used duraweb®SG2 bags. Thus bags require disinfecting and cleaning before re-use. It is concluded that nonwoven synthetic bags are a better choice than the Kraft paper pollination bags for increasing the grain yield and virtually eliminating the bird damage in sorghum
Optical injection and terahertz detection of the macroscopic Berry curvature
We propose an experimental scheme to probe the Berry curvature of solids. Our
method is sensitive to arbitrary regions of the Brillouin zone, and employs
only basic optical and terahertz techniques to yield a background free signal.
Using semiconductor quantum wells as a prototypical system, we discuss how to
inject Berry curvature macroscopically, and probe it in a way that provides
information about the underlying microscopic Berry curvature.Comment: 4 pages, accepted in Physical Review Letter
Additive Equivalence in Turbulent Drag Reduction by Flexible and Rodlike Polymers
We address the "Additive Equivalence" discovered by Virk and coworkers: drag
reduction affected by flexible and rigid rodlike polymers added to turbulent
wall-bounded flows is limited from above by a very similar Maximum Drag
Reduction (MDR) asymptote. Considering the equations of motion of rodlike
polymers in wall-bounded turbulent ensembles, we show that although the
microscopic mechanism of attaining the MDR is very different, the macroscopic
theory is isomorphic, rationalizing the interesting experimental observations.Comment: 8 pages, PRE, submitte
Study of optical band gap and carbon cluster sizes formed in 100 MeV Si8+ and 145 MeV Ne6+ ions irradiated polypropylene polymer
A wide variety of material modifications in polymers have been studied by using ion irradiation
techniques. Extensive research has focused on to Swift Heavy Ions (MeV's energy), probably because of good
controllability and the large penetration length in polymers. High energy ion irradiation tends to damage polymers
significantly by electronic excitation and ionization. It may result into the creation of latent tracks and can also
cause formation of radicals such as ablation, sputtering, chain scission and intermolecular cross-linking, creation
of triple bonds and unsaturated bonds and loss volatile fragments. Polypropylene polymer films of thickness 50
μm were irradiated to the fluences of 1 × 1010, 3 × 1010, 1 × 1011, 3 × 1011, 6 × 1011 and 1 × 1012 ions/cm2 with Si8+
ions of 100 MeV energy from Pelletron accelerator at Inter University Accelerator Centre (IUAC), New Delhi and
Ne6+ ions of 145 MeV to the fluences of 108, 1010, 1011, 1012 and 1013 ions/cm3 from Variable Energy Cyclotron
Centre, Kolkata. Optical modifications were characterized by UV towards the red end of the spectrum with the
increase of the fluence. Value of optical band gap Eg shows a decreasing trend with ion fluence irradiated with
both kinds of ions. Cluster size N, the number of carbon atoms per conjugation length increases with increasing
ion dose. Cluster size also increases with the increase of electronic stopping power.Rajesh Kumar1*, S Asad Ali1, A. H. Naqvi1, H. S. Virk2, Udayan De3,
D K Avasthi4 and Rajendra Prasad1
1Department of Applied Physics, Z. H. College of Engineering & Technology,
Aligarh Muslim University, Aligarh-202 002, Uttar Pradesh, India
2360 Sector-71, SAS Nagar (Mohali), Chandigarh-160 071, Punjab, India
3Variable Energy Cyclotron Centre, 1/AF, Bidhan Nagar, Kolkata-700 064, India
4Inter-University Accelerator Centre, Aruna Asaf Ali Marg, New Delhi-110 067, India
E-mail : [email protected] of Applied Physics, Z. H. College of Engineering & Technology,
Aligarh Muslim University, Aligarh-202 002, Uttar Pradesh, India
2360 Sector-71, SAS Nagar (Mohali), Chandigarh-160 071, Punjab, India
Variable Energy Cyclotron Centre, 1/AF, Bidhan Nagar, Kolkata-700 064, India
Inter-University Accelerator Centre, Aruna Asaf Ali Marg, New Delhi-110 067, Indi
Toward a structural understanding of turbulent drag reduction: nonlinear coherent states in viscoelastic shear flows
Nontrivial steady flows have recently been found that capture the main
structures of the turbulent buffer layer. We study the effects of polymer
addition on these "exact coherent states" (ECS) in plane Couette flow. Despite
the simplicity of the ECS flows, these effects closely mirror those observed
experimentally: Structures shift to larger length scales, wall-normal
fluctuations are suppressed while streamwise ones are enhanced, and drag is
reduced. The mechanism underlying these effects is elucidated. These results
suggest that the ECS are closely related to buffer layer turbulence.Comment: 5 pages, 3 figures, published version, Phys. Rev. Lett. 89, 208301
(2002
Giant ambipolar Rashba effect in a semiconductor: BiTeI
We observe a giant spin-orbit splitting in bulk and surface states of the
non-centrosymmetric semiconductor BiTeI. We show that the Fermi level can be
placed in the valence or in the conduction band by controlling the surface
termination. In both cases it intersects spin-polarized bands, in the
corresponding surface depletion and accumulation layers. The momentum splitting
of these bands is not affected by adsorbate-induced changes in the surface
potential. These findings demonstrate that two properties crucial for enabling
semiconductor-based spin electronics -- a large, robust spin splitting and
ambipolar conduction -- are present in this material.Comment: 4 pages, 3 figure
Transition From Targeted Breeding to Mainstreaming of Biofortification Traits in Crop Improvement Programs
Biofortification breeding for three important micronutrients for human health, namely,
iron (Fe), zinc (Zn), and provitamin A (PVA), has gained momentum in recent years.
HarvestPlus, along with its global consortium partners, enhances Fe, Zn, and PVA
in staple crops. The strategic and applied research by HarvestPlus is driven by
product-based impact pathway that integrates crop breeding, nutrition research, impact
assessment, advocacy, and communication to implement country-specific crop delivery
plans. Targeted breeding has resulted in 393 biofortified crop varieties by the end of
2020, which have been released or are in testing in 63 countries, potentially benefitting
more than 48 million people. Nevertheless, to reach more than a billion people by 2030,
future breeding lines that are being distributed by Consultative Group on International
Agricultural Research (CGIAR) centers and submitted by National Agricultural Research
System (NARS) to varietal release committees should be biofortified. It is envisaged that
the mainstreaming of biofortification traits will be driven by high-throughput micronutrient
phenotyping, genomic selection coupled with speed breeding for accelerating genetic
gains. It is noteworthy that targeted breeding gradually leads to mainstreaming, as the
latter capitalizes on the progress made in the former. Efficacy studies have revealed the
nutritional significance of Fe, Zn, and PVA biofortified varieties over non-biofortified ones.
Mainstreaming will ensure the integration of biofortified traits into competitive varieties
and hybrids developed by private and public sectors. The mainstreaming strategy has
just been initiated in select CGIAR centers, namely, International Maize and Wheat
Improvement Center (CIMMYT), International Rice Research Institute (IRRI), International
Crops Research Institute for the Semi-Arid Tropics (ICRISAT), International Institute of
Tropical Agriculture (IITA), and International Center for Tropical Agriculture (CIAT). This
review will present the key successes of targeted breeding and its relevance to the
mainstreaming approaches to achieve scaling of biofortification to billions sustainably
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