Forecasting phenology of mustard crop in North-western Himalayas

Field experiments were conducted during rabiseason of 2007-08 and 2008-09 to study the phenology, thermal indices and its subsequent effect on dry matter accumulation of mustard (Brassica juncea L.) varieties viz., RCC-4, Kranti and Varuna grown under varying environmental conditions of Himachal Pradesh. The early sown (10th October) crop varieties took maximum average growing degree days for flower initiation (492±1), 50% flower-ing (682±1), pod initiation (742±1), 90% pod formation (811±4) and maturity (1394±8) which decreased with subse-quent delay in sowing time and recorded lowest under late sown (9th November) crop. The accumulated helio-thermal units and photo-thermal units decreased from 9824 to 7467 oC day hour and 19074 to 15579 oC day hour, respectively. High heat-use efficiency was obtained under late sown condition on 30th October. The heat-use efficiency (HUE) was high at 90% pod formation stage as compared to other stages in all the varieties and sowing dates (except 9th November sowing). The early sown (10th October) crop had maximum calendar days and cumula-tive pan evaporation (158 days and 448.2 mm) followed by normal (20th and 30th October) (153 days and 434 mm) and late (9th November) (138 days and 403.1 mm) sown crop indicating higher water requirement under early sow-ing. The predictive regression models explained 83-85% variation in dry matter yield in three varieties of mustard. The agro climatic indices are important determinants for temperature, radiations and photoperiods behaviors of crop. The accurate predictions of crop phenology are useful inputs for crop simulation modeling and crop management, and used for climate change assessment and simulated adaptations in present scenarios

Real space iterative reconstruction for vector tomography (RESIRE-V)

Tomography has had an important impact on the physical, biological, and medical sciences. To date, most tomographic applications have been focused on 3D scalar reconstructions. However, in some crucial applications, vector tomography is required to reconstruct 3D vector fields such as the electric and magnetic fields. Over the years, several vector tomography methods have been developed. Here, we present the mathematical foundation and algorithmic implementation of REal Space Iterative REconstruction for Vector tomography, termed RESIRE-V. RESIRE-V uses multiple tilt series of projections and iterates between the projections and a 3D reconstruction. Each iteration consists of a forward step using the Radon transform and a backward step using its transpose, then updates the object via gradient descent. Incorporating with a 3D support constraint, the algorithm iteratively minimizes an error metric, defined as the difference between the measured and calculated projections. The algorithm can also be used to refine the tilt angles and further improve the 3D reconstruction. To validate RESIRE-V, we first apply it to a simulated data set of the 3D magnetization vector field, consisting of two orthogonal tilt series, each with a missing wedge. Our quantitative analysis shows that the three components of the reconstructed magnetization vector field agree well with the ground-truth counterparts. We then use RESIRE-V to reconstruct the 3D magnetization vector field of a ferromagnetic meta-lattice consisting of three tilt series. Our 3D vector reconstruction reveals the existence of topological magnetic defects with positive and negative charges. We expect that RESIRE-V can be incorporated into different imaging modalities as a general vector tomography method

Evaluation of white grain maize varieties for growth, yield and yield components

Maize (Zea mays L.)  is one of the most commonly cultivated crop after rice in Nepal. The present study was done to evaluate and recommend the best performing white maize genotypes in mid hill region of Nepal. This study was conducted at research field of Kavre, Nepal during the rainy season of 2019. Five white maize genotypes were evaluated in randomized complete block design with four replications where Deuti used as standard check. Ear and plant height of plant, days to 50% silking and tasseling, count of leaf above and below main cob, total number of leaf, cob length, cob diameter, kernel rows per cob, kernels count per row, thousand kernels weight, shelling and sterility percentage, stay green and grain yield parameters were observed. Deuti and DMH-7314 had good stay green and husk cover rating. Plant height (282.6 cm) and ear height (162.4 cm) was more in HB-008. Number of kernels per row was more in HB-008 (36.5) and HB-007 (36.5) and thousand kernel weights was more in DMH-7314 (386.3 g) followed by Deuti (353.9 g). DMH-7314 was late in tasseling (86 days) and silking (89 days) but shelling percentage was lowest in DMH-7314 (70.8) than other varieties. Analysis of variance reveled that genotype HB-008 (9.70 t/ha) as compared to standard check Deuti (7.80 t/ha). Thus genotype HB-008 perform better in mid hill region of Kavre, Nepal

GENFIRE: A generalized Fourier iterative reconstruction algorithm for high-resolution 3D imaging

Tomography has made a radical impact on diverse fields ranging from the study of 3D atomic arrangements in matter to the study of human health in medicine. Despite its very diverse applications, the core of tomography remains the same, that is, a mathematical method must be implemented to reconstruct the 3D structure of an object from a number of 2D projections. In many scientific applications, however, the number of projections that can be measured is limited due to geometric constraints, tolerable radiation dose and/or acquisition speed. Thus it becomes an important problem to obtain the best-possible reconstruction from a limited number of projections. Here, we present the mathematical implementation of a tomographic algorithm, termed GENeralized Fourier Iterative REconstruction (GENFIRE). By iterating between real and reciprocal space, GENFIRE searches for a global solution that is concurrently consistent with the measured data and general physical constraints. The algorithm requires minimal human intervention and also incorporates angular refinement to reduce the tilt angle error. We demonstrate that GENFIRE can produce superior results relative to several other popular tomographic reconstruction techniques by numerical simulations, and by experimentally by reconstructing the 3D structure of a porous material and a frozen-hydrated marine cyanobacterium. Equipped with a graphical user interface, GENFIRE is freely available from our website and is expected to find broad applications across different disciplines.Comment: 18 pages, 6 figure

In situ coherent diffractive imaging

Coherent diffractive imaging (CDI) has been widely applied in the physical and biological sciences using synchrotron radiation, XFELs, high harmonic generation, electrons and optical lasers. One of CDI's important applications is to probe dynamic phenomena with high spatio-temporal resolution. Here, we report the development of a general in situ CDI method for real-time imaging of dynamic processes in solution. By introducing a time-invariant overlapping region as a real-space constraint, we show that in situ CDI can simultaneously reconstruct a time series of the complex exit wave of dynamic processes with robust and fast convergence. We validate this method using numerical simulations with coherent X-rays and performing experiments on a materials science and a biological specimen in solution with an optical laser. Our numerical simulations further indicate that in situ CDI can potentially reduce the radiation dose by more than an order of magnitude relative to conventional CDI. As coherent X-rays are under rapid development worldwide, we expect in situ CDI could be applied to probe dynamic phenomena ranging from electrochemistry, structural phase transitions, charge transfer, transport, crystal nucleation, melting and fluid dynamics to biological imaging.Comment: 19 pages, 5 figure

Single-shot 3D coherent diffractive imaging of core-shell nanoparticles with elemental specificity.

We report 3D coherent diffractive imaging (CDI) of Au/Pd core-shell nanoparticles with 6.1 nm spatial resolution with elemental specificity. We measured single-shot diffraction patterns of the nanoparticles using intense x-ray free electron laser pulses. By exploiting the curvature of the Ewald sphere and the symmetry of the nanoparticle, we reconstructed the 3D electron density of 34 core-shell structures from these diffraction patterns. To extract 3D structural information beyond the diffraction signal, we implemented a super-resolution technique by taking advantage of CDI's quantitative reconstruction capabilities. We used high-resolution model fitting to determine the Au core size and the Pd shell thickness to be 65.0 ± 1.0 nm and 4.0 ± 0.5 nm, respectively. We also identified the 3D elemental distribution inside the nanoparticles with an accuracy of 3%. To further examine the model fitting procedure, we simulated noisy diffraction patterns from a Au/Pd core-shell model and a solid Au model and confirmed the validity of the method. We anticipate this super-resolution CDI method can be generally used for quantitative 3D imaging of symmetrical nanostructures with elemental specificity

Multimodal x-ray and electron microscopy of the Allende meteorite.

Multimodal microscopy that combines complementary nanoscale imaging techniques is critical for extracting comprehensive chemical, structural, and functional information, particularly for heterogeneous samples. X-ray microscopy can achieve high-resolution imaging of bulk materials with chemical, magnetic, electronic, and bond orientation contrast, while electron microscopy provides atomic-scale spatial resolution with quantitative elemental composition. Here, we combine x-ray ptychography and scanning transmission x-ray spectromicroscopy with three-dimensional energy-dispersive spectroscopy and electron tomography to perform structural and chemical mapping of an Allende meteorite particle with 15-nm spatial resolution. We use textural and quantitative elemental information to infer the mineral composition and discuss potential processes that occurred before or after accretion. We anticipate that correlative x-ray and electron microscopy overcome the limitations of individual imaging modalities and open up a route to future multiscale nondestructive microscopies of complex functional materials and biological systems