463 research outputs found
Large amplitude solitary waves in ion-beam plasmas with charged dust impurities
The nonlinear propagation of large amplitude dust ion-acoustic (DIA) solitary
waves (SWs) in an ion-beam plasma with stationary charged dusts is
investigated. For typical plasma parameters relevant for experiments [J. Plasma
Phys. \textbf{60}, 69 (1998)], when the beam speed is larger than the DIA speed
(), three stable waves, namely the "fast" and "slow"
ion-beam modes and the plasma DIA wave are shown to exist. These modes can
propagate as SWs in the beam plasmas. However, in the other regime
(), one of the beam modes when coupled to the DIA mode may
become unstable. The SWs with positive (negative) potential may exist when the
difference of the nonlinear wave speed () and the beam speed is such that
(). Furthermore, for real
density perturbations, the wave potential is found to be limited by a
critical value which typically depends on , as well as the ion/beam
temperature. The conditions for the existence of DIA solitons are obtained and
their properties are analyzed numerically in terms of the system parameters.
While the system supports both the compressive and rarefactive large amplitude
SWs, the small amplitude solitons exist only of the compressive type. The
theoretical results may be useful for observation of soliton excitations in
laboratory ion-beam driven plasmas as well as in space plasmas where the
charged dusts play as impurities.Comment: 8 pages, 6 figures; Article to appear in Phys. Plasmas (2011
Analysis of a model with a common source of CP violation
We work in a model where all CP violating phenomena have a common source. CP
is spontaneously broken at a large scale through the phase of a complex
singlet scalar. An additional singlet vector-like down-type quark
relates this high scale CP violation to low energy. We quantitatively analyze
this model in the quark sector. We obtain the numerical values of the
parameters of the Lagrangian in the quark sector for a specific ansatz of the
down-type quark mass matrix where the weak phase is generated
minimally. vertex will modify in presence of the extra vector-like
down-type quark. From the experimental lower bound of the partial decay width
we find out the lower bound of the additional down-type quark
mass. Tree level flavor changing neutral current appears in this model due to
the presence of the extra vector-like down-type quark. We give the range of
values of the mass splitting in system
using SM box, mediating tree level and mediating one loop diagrams
together for both . We find out the analytical expression for
in this model from standard box, and Higgs mediated penguin
diagrams for system, . From this we numerically
evaluate the decay width difference . We
also find out the numerical values of the CP asymmetry parameters and
for the decays and
respectively. We get the lower bound of the scale through the upper bound
of the strong CP phase.Comment: 20 pages, no figures New materials and references have been added.
Text has been modified. To be appear in J.Phys.
Ion-acoustic solitary waves and shocks in a collisional dusty negative ion plasma
We study the effects of ion-dust collisions and ion kinematic viscosities on
the linear ion-acoustic instability as well as the nonlinear propagation of
small amplitude solitary waves and shocks (SWS) in a negative ion plasma with
immobile charged dusts. {The existence of two linear ion modes, namely the
`fast' and `slow' waves is shown, and their properties are analyzed in the
collisional negative ion plasma.} {Using the standard reductive perturbation
technique, we derive a modified Korteweg-de Vries-Burger (KdVB) equation which
describes the evolution of small amplitude SWS.} {The profiles of the latter
are numerically examined with parameters relevant for laboratory and space
plasmas where charged dusts may be positively or negatively charged.} It is
found that negative ion plasmas containing positively charged dusts support the
propagation of SWS with negative potential. However, the perturbations with
both positive and negative potentials may exist when dusts are negatively
charged. The results may be useful for the excitation of SWS in laboratory
negative ion plasmas as well as for observation in space plasmas where charged
dusts may be positively or negatively charged.Comment: 13 pages, 9 figures; To appear in Physical Review
Management strategy for leaf blight of cabbage (Brassica oleracea var. capitata L.) in foothills of Nagaland
Cabbage (Brassica oleracea var. capitata L.) is a major cole crop in India. Cabbage leaf blight caused by Alternaria sp. is one of the serious foliar diseases responsible for low production and productivity. The disease is challenging to manage alone with fungicides or bioagents. Hence, the present study was undertaken to manage the disease effectively by utilizing bioagents, fungicides, and their combinations. The field trial was carried out in the Horticultural Research Farm, School of Agricultural Sciences, Nagaland University, Medziphema, Nagaland, during Rabi, 2022-2023 and in vitro evaluation of fungicides and bioagents conducted in the Department of Plant Pathology, School of Agricultural Sciences, Nagaland University, Medziphema, Nagaland. Management of leaf blight of cabbage was conducted with seven treatments (T1-T7). Among the different treatments tested in field condition, the minimum severity of Alternaria leaf blight (37.69%) coupled with maximum yield (23.39 t/ha) with a higher-cost benefit ratio of 2.72 were recorded in T6 (seed treatment with captan @ 3 g/kg + four foliar sprays of azoxystrobin 4.8% + chlorothalonil @ 0.25%). Among the six treatments, In vitro evaluation of bioagents Trichoderma sp. (TTV-2; T5) showed maximum inhibition with 69.44%, followed by Bacillus subtilis (CRB-7; T6) with 31.11% inhibition and among the chemical fungicides, azoxystrobin (amistar) showed the highest inhibition of 76.67% as compared to control. These treatments can effectively manage cabbage leaf blight disease and ensure sustained yields, particularly in the foothills of Nagaland.
Debris cover and surface melt at a temperate maritime alpine glacier: Franz Josef Glacier, New Zealand
Melt rates on glaciers are strongly influenced by the presence of supraglacial debris, which can either enhance or reduce ablation relative to bare ice. Most recently, Franz Josef Glacier has entered into a phase of strong retreat and downwasting, with the increasing emergence of debris on the surface in the ablation zone. Previously at Franz Josef Glacier, melt has only been measured on bare ice. During February 2012, a network of 11 ablation stakes was drilled into locations of varying supraglacial debris thickness on the lower glacier. Mean ablation rates over 9 days varied over the range 1.2–10.1 cm d−1, and were closely related to debris thickness. Concomitant observations of air temperature allowed the application of a degree-day approach to the calculation of melt rates, with air temperature providing a strong indicator of melt. Degree-day factors (d f) varied over the range 1.1–8.1 mm d−1 °C−1 (mean of 4.4 mm d−1 °C−1), comparable with rates reported in other studies. Mapping of the current debris cover revealed 0.7 km2 of the 4.9 km2 ablation zone surface was debris-covered, with thicknesses ranging 1–50 cm. Based on measured debris thicknesses and d f, ablation on debris-covered areas of the glacier is reduced by a total of 41% which equates to a 6% reduction in melt overall across the entire ablation zone. This study highlights the usefulness of a short-term survey to gather representative ablation data, consistent with numerous overseas ablation studies on debris-covered glaciers
Stochastic model for drought forecasting for Bundelkhand region in Central India
In the present study, standardized precipitation index (SPI) series at 3-month, 6-month, 9-month, 12-month and 24month time scale has been used to assess the vulnerability of meteorological drought in the Bundelkhand region of Central India. SPI values revealed that the droughts in the region over the study period vary from moderately high to extremely high. Suitable linear stochastic model, viz. seasonal and non-seasonal autoregressive integrated moving average (ARIMA) developed to predict drought at different time scale. The best model was selected based on minimum Akaike Information Criterion (AIC) and Schwarz Bayesian Criterion (SBC). Statistical analysis revealed that non-seasonal ARIMA model was appropriate for 3-month SPI series while seasonal ARIMA models have been found promising for SPI series at 6-, 9,12 and 24-month time scale. Parameter estimation step indicates that the estimated model parameters are significantly different from zero. The predicted data using the best ARIMA model were compared to the observed data for model validation purpose in which the predicted data show reasonably good agreement with the actual data. Hence the models were applied to forecast drought in the Bundelhand region up to 3 months advanced with good accuracy
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