Comment on "Spin Transport properties of the quantum one-dimensional non-linear sigma model"

In a recent preprint (cond-mat/9905415), Fujimoto has used the Bethe ansatz to compute the finite temperature, zero frequency Drude weight of spin transport in the quantum O(3) non-linear sigma model in a magnetic field $H \neq 0$. We show here that, contrary to his claims, the results are in accord with earlier semiclassical results (Sachdev and Damle, cond-mat/9610115). We also comment on his 1/N expansion, and show that it does not properly describe the long-time correlations.Comment: 4 page

Intermediate temperature dynamics of one-dimensional Heisenberg antiferromagnets

We present a general theory for the intermediate temperature (T) properties of Heisenberg antiferromagnets of spin-S ions on p-leg ladders, valid for 2Sp even or odd. Following an earlier proposal for 2Sp even (Damle and Sachdev, cond-mat/9711014), we argue that an integrable, classical, continuum model of a fixed-length, 3-vector applies over an intermediate temperature range; this range becomes very wide for moderate and large values of 2Sp. The coupling constants of the effective model are known exactly in terms of the energy gap above the ground state (for 2Sp even) or a crossover scale (for 2Sp odd). Analytic and numeric results for dynamic and transport properties are obtained, including some exact results for the spin-wave damping. Numerous quantitative predictions for neutron scattering and NMR experiments are made. A general discussion on the nature of T>0 transport in integrable systems is also presented: an exact solution of a toy model proves that diffusion can exist in integrable systems, provided proper care is taken in approaching the thermodynamic limit.Comment: 38 pages, including 12 figure

17O NMR study of q=0 spin excitations in a nearly ideal S=1/2 1D Heisenberg antiferromagnet, Sr2CuO3, up to 800 K

We used 17O NMR to probe the uniform (wavevector q=0) electron spin excitations up to 800 K in Sr2CuO3 and separate the q=0 from the q=\pm\pi/a staggered components. Our results support the logarithmic decrease of the uniform spin susceptibility below T ~ 0.015J, where J=2200 K. From measurement of the dynamical spin susceptibility for q=0 by the spin-lattice relaxation rate 1/T_{1}, we demonstrate that the q=0 mode of spin transport is ballistic at the T=0 limit, but has a diffusion-like contribution at finite temperatures even for T << J.Comment: Submitted to Phys. Rev. Lett. 4 pages, 4 figure

Farmers’ Perception on Constraints in Adoption of Double Cropping in Upper Brahmaputra Valley Zone of Assam

Introduction: Out of the total net cropped area of 28.10 lakh hectares in Assam, only 1.96 lakh hectares is under double cropping despite the implementation of “Mission Double Cropping†with a fixed target of covering 2.09 lakh hectares in the state. Double cropping is not a new concept in Assam, because the cropping intensity has increased to 155.81 percent in 2013-14 from 152.29 percent in 2012-13. However, there is still some inhibitions on the part of the farmers in going for double cropping though it gives the farmers an increasing cash flow. Aims: The present study was conducted to identify the major socio-economic constraints in adoption of double cropping. Study Design: Original Research. Place and Duration of Study: The study was conducted in Jorhat and Golaghat districts of Upper Brahmaputra Valley Zone (UBVZ) of Assam during 2016 where government programmes of double cropping are in operation. Methodology: The study was based on primary data collected through the personal interview from a sample of 120 farmers. The sample was drawn through multistage stratified random sampling technique. Constraint facing index was used. Results: The study revealed the non-availability of water supply in the crop field as the major constraint faced by the highest number of farmers during Rabi season followed by a shortage of labour and stray cattle problem. Some other problems such as non-availability of credit, shortage of water supply to the crop field, high fuel cost, shortage of credit, high wage rate, transportation cost were also reported by the study as constraints in adopting double cropping in the zone. Conclusion: The study suggested some measures to overcome these reported problems like ensuring adequate irrigation facilities, proper awareness among the famers regarding water harvesting, proper fencing around the field to avoid stray cattle etc

Mechanistic insight into the sensing of nitroaromatic compounds by metal-organic frameworks

There has been extensive research on the sensing of explosive nitroaromatic compounds (NACs) using fluorescent metal-organic frameworks (MOFs). However, ambiguity in the sensing mechanism has hampered the development of efficient explosive sensors. Here we report the synthesis of a hydroxyl-functionalized MOF for rapid and efficient sensing of NACs and examine in detail its fluorescence quenching mechanisms. In chloroform, quenching takes place primarily by exciton migration to the ground-state complex formed between the MOF and the analytes. A combination of hydrogen-bonding interactions and ??????? stacking interactions are responsible for fluorescence quenching, and this observation is supported by single-crystal structures. In water, the quenching mechanism shifts toward resonance energy transfer and photo-induced electron transfer, after exciton migration as in chloroform. This study provides insight into florescence-quenching mechanisms for the selective sensing of NACs and reduces the ambiguity regarding the nature of interactions between the MOF and NACs

Quantum impurity dynamics in two-dimensional antiferromagnets and superconductors

We present the universal theory of arbitrary, localized impurities in a confining paramagnetic state of two-dimensional antiferromagnets with global SU(2) spin symmetry. The energy gap of the host antiferromagnet to spin-1 excitations, \Delta, is assumed to be significantly smaller than a typical nearest neighbor exchange. In the absence of impurities, it was argued in earlier work (Chubukov et al. cond-mat/9304046) that the low-temperature quantum dynamics is universally and completely determined by the values of \Delta and a spin-wave velocity c. Here we establish the remarkable fact that no additional parameters are necessary for an antiferromagnet with a dilute concentration of impurities, n_{imp} - each impurity is completely characterized by a integer/half-odd-integer valued spin, S, which measures the net uncompensated Berry phase due to spin precession in its vicinity. We compute the impurity-induced damping of the spin-1 collective mode of the antiferromagnet: the damping occurs on an energy scale \Gamma= n_{imp} (\hbar c)^2/\Delta, and we predict a universal, asymmetric lineshape for the collective mode peak. We argue that, under suitable conditions, our results apply unchanged (or in some cases, with minor modifications) to d-wave superconductors, and compare them to recent neutron scattering experiments on YBCO by Fong et al. (cond-mat/9812047). We also describe the universal evolution of numerous measurable correlations as the host antiferromagnet undergoes a quantum phase transition to a Neel ordered state.Comment: 36 pages, 12 figures; added reference

Effect of fermented liquid feed on feed efficiency, gut health and immunity of Large White Yorkshire (LWY) fattener pigs

The study assessed effect of fermented liquid feed (FLF) on feed efficiency, gut health and immunity of LWY fattener pigs. Weaned piglets (24) were assigned four dietary treatments (T1, T2, T3, T4) in two phases in a randomised block design for 180 days. T1 was fed standard ration (SR), T2 was fed SR mixed with water (1:2, w/w), T3 and T4 were fed FLF fermented by Lactobacillus acidophilus (T3) and Enterococcus faecium (T4) respectively. Feed efficiency was calculated fortnightly; diarrhoea score and incidence up to day 14; faecal pH, NH3-N, lactic acid, LAB, Escherichia coli and Salmonella on day 1, 60, 120 and 180; immune responses and histomorphology of small intestine at 42nd day. Final body weight and gain, feed efficiency was significantly higher in T3 and T4. The DS and DI reduced significantly in T3 and T4. Increased faecal pH and reduced NH3-N recorded in T3 and T4 on 180th and 120th day respectively. Faecal LAB was significantly higher on 120th day and increasing trends on 60th and 108th day recorded in T3 and T4. Faecal Escherichia coli and Salmonella was significantly reduced in T3 and T4. Increased VH, decreased CD and higher AVSA with infiltration of mononuclear and lymphoid follicles observed in T3 and T4. Antibody titre (HI log10/ml) on 7th and 21st day post-inoculation was recorded significantly higher in T3 and T4. Based on findings of the study, feeding of FLF by Lactobacillus acidophilus or Enterococcus faecium was recommended to LWY fattener pigs

Effects of Soret, Dufour, Variable Viscosity and Variable Thermal Conductivity on Unsteady Free Convective Flow Past a Vertical Cone

Abstract In this paper investigation have been carried out on Soret and Dufour effects, variable viscosity and variable thermal conductivity effects on unsteady free convective flow past a vertical cone. Here a mathematical model is considered on unsteady free convective flow over an incompressible fluid past a vertical cone with nonuniform surface temperature and concentration. The governing partial differential equations are altered into dimensionless form, and then solved numerically by an iterative technique based on finite difference scheme. The velocity, the temperature and the concentration profile have been drawn for various values of Soret number, Dufour number, time, viscosity parameter and thermal conductivity parameter. The local skin friction is also studied for various parameters

Effect of Sowing Media and Variety on Seedling Root Growth and Field Performance of Early Cauliflower (Brassica oleracea var. botrytis)

An experiment was conducted inside greenhouse and in the field of the Experimental Farm, Department of Horticulture, College of Agriculture, Assam Agricultural University, Jorhat for two consecutive years (2018 and 2019) to assess the effect of sowing media and variety  on root growth of  early cauliflower seedling and subsequent performance of seedling  in the main field. The experiment was laid out in Factorial Randomized Block Design with eight treatments comprising of four sowing media [M1-cocopeat (60%): vermiculite (20%): perlite (20%), M2-cocopeat (50%): vermicompost (50%), M3-cocopeat (50%): vermicompost (50%): microbial consortium and M4-Conventional nursery] and two varieties [V1 (White Diamond) and V2 (CFL1522)] replicated thrice. Treatment M1, M2 and M3 were inside green house. The results revealed root parameters at seedling stage were significantly influenced by sowing media. The highest root length (4.94 cm), root fresh weight (0.26 mg) and root dry weight (0.07 mg) of seedling were recorded in M3. Between the two varieties (i.e V1 and V2) V1 exhibited the maximum root length (4.24 cm) while no significant difference was observed for root fresh and dry weight. Among interactions, M2V1 recorded maximum root length (5.83 cm) while M3V1 recorded maximum root fresh weight (0.28 mg) and dry weight (0.08 mg) of seedling. After transplanting in the field, significant variations for root parameters were observed. Cauliflower plants that were grown in M3 at seedling stage recorded highest root length (21.94 cm) and  volume (74.59 cm3) but for root dry weight  seedlings that were grown in M2  recorded maximum  dry weight i.e. 3.28 g. Variety V2 recorded maximum root length (17.76 cm) and dry weight (2.68 g).  M3V2   recorded highest root length (22.01 cm), volume (76.46 cm3) and dry weight (3.48 g). Curd characters were also significantly influence by media while variety showed significant variation for days to curd initiation, harvesting and curd diameter only. M3 recorded minimum days for curd initiation and harvesting (37.09 and 53.26), maximum curd compactness (53.05 g/cm3), diameter (12.84 cm), weight (0.41 kg) and shelf life (8.89 days).The interaction effect between media and variety was also found significant. The combination M3V1 recorded  minimum days  for curd initiation and harvesting ((36.55 and 52.32), maximum curd compactness (53.15 g/cm3)  while M3V2 recorded maximum curd  diameter (13.51 cm), curd weight (0.41 kg) and shelf life (9.50 days) .The  combination M4V2  recorded maximum days  for curd initiation and harvesting (45.46 and 63.87),minimum curd compactness (42.77 g/cm3)  and M4V1 recorded minimum curd diameter (10.28 cm), shelf life (4.95 days)  while  both  M4V1 and M4V2 recorded minimum curd weight (0.27 kg). From the present investigation it can be concluded that for producing quality seedlings in the nursery which will further show good performance in the field seedling can be raised in media(M3) i.e.cocopeat (50): vermicompost (50): microbial consortium @ 1:100 under protected condition

Parametrization of nonlinear and chaotic oscillations in driven beam-plasma diodes

Nonlinear phenomena in a driven plasma diode are studied using a fluid code and the particle-in-cell simulation code XPDPI. When a uniform electron beam is injected to a bounded diode filled with uniform ion background, the beam is destabilized by the Pierce instability and a perturbation grows to exhibit nonlinear oscillations including chaos. Two standard routes to chaos, period doubling and quasiperiodicity, are observed. Mode lockings of various winding numbers are observed in an ac driven system. A new diagnostic quantity is used to parametrize various nonlinear oscillations.open10