Quasi-static remanence as a generic-feature of spin-canting in Dzyaloshinskii-Moriya Interaction driven canted-antiferromagnets

We consistently observe a unique pattern in remanence in a number of canted-antiferromagnets (AFM) and piezomagnets. A part of the remanence is $\textit{quasi-static}$ in nature and vanishes above a critical magnetic field. Present work is devoted to exploring this $\textit{quasi-static}$ remanence ($\mu$) in a series of isostructural canted-AFMs and piezomagnets that possess progressively increasing N\'eel temperature ($T{_N}$). Comprehensive investigation of remanence as a function of $\textit{magnetic-field}$ and $\textit{time}$ in CoCO$_{3}$, NiCO$_{3}$ and MnCO$_{3}$ reveals that the magnitude of $\mu$ increases with decreasing $T{_N}$, but the stability with time is higher in the samples with higher $T{_N}$. Further to this, all three carbonates exhibit a universal scaling in $\mu$, which relates to the concurrent phenomenon of piezomagnetism. Overall, these data not only establish that the observation of $\textit{quasi-static}$ remanence with $\textit{counter-intuitive}$ magnetic-field dependence can serve as a foot-print for spin-canted systems, but also confirms that simple remanence measurements, using SQUID magnetometry, can provide insights about the extent of spin canting - a non trivial parameter to determine. In addition, these data suggest that the functional form of $\mu$ with $\textit{magnetic-field}$ and $\textit{time}$ may hold key to isolate Dzyaloshinskii Moriya Interaction driven spin-canted systems from Single Ion Anisotropy driven ones. We also demonstrate the existence of $\mu$ by tracking specific peaks in neutron diffraction data, acquired in remnant state in CoCO$_{3}$

Sol gel synthesis and photoluminescence study of Eu3+ doped SnO2

Tin oxide(IV) nanophosphor doped with europium had been prepared by sol-gel technique using SnCl4 as precurser. XRD, IR, SEMand TEM analyses were used for characterization of SnO2:Eu3+. The XRD analysis shows that well crystallized tetragonal rutile SnO2:Eu3+ can be obtained by this method and the crystal size was about 15-20nm as an average for the sample calcined at 400ºC for 2h. The evolution of the most important functional groups during the steps involved in this synthesis route is explained in view of the results obtained with FTIR and XRD.  A spherical like morphology of the prepared  SnO2 nanoparticles was observed in the SEM and TEM studies. The SnO2 nanoparticles show stable photoluminescence emission intensity at 612 nm (5D0/7F2) of the Eu3+ ions activated SnO2 nanocrystals  This paper discuss the mechanistic approach of origin of luminescence in SnO2

Using positional information to provide context for biological image analysis with MorphoGraphX 2.0

Positional information is a central concept in developmental biology. In developing organs, positional information can be idealized as a local coordinate system that arises from morphogen gradients controlled by organizers at key locations. This offers a plausible mechanism for the integration of the molecular networks operating in individual cells into the spatially-coordinated multicellular responses necessary for the organization of emergent forms. Understanding how positional cues guide morphogenesis requires the quantification of gene expression and growth dynamics in the context of their underlying coordinate systems. Here we present recent advances in the MorphoGraphX software (Barbier de Reuille et al., 2015)⁠ that implement a generalized framework to annotate developing organs with local coordinate systems. These coordinate systems introduce an organ-centric spatial context to microscopy data, allowing gene expression and growth to be quantified and compared in the context of the positional information thought to control them

Cell Lineage Tracking. Implementation of automated lineage tracking on 4D confocal image data in the MorphoGraphX software.

Multicellular organisms comprise a multitude of cells belonging to diverse types. The cells undergo growth and differentiation to generate tissues and develop the shape of organs. This phenomenon is known as morphogenesis. In order to study morphogenesis, temporal analysis of cell populations in an organism is studied which requires the determination of cell lineage. This problem is generally known as lineage tracking. MorphoGraphX is a software used by biologists to study various aspects of morphogenesis, specifically in plant samples, as it enables visualization and analysis of 3D biological datasets or images obtained from confocal microscopy. Despite the importance of lineage tracking to study morphogenesis, it is not automated in the software. Its automation in the software is a challenging problem due to irregularities among the cells with respect to their behaviour, shape and division. However, its implementation would improve efficiency and make it feasible to track lineage in a wider variety of datasets. In the current work, a software is implemented to automate lineage tracking in MorphoGraphX. The method does a piecewise linear registration of the meshes (2D curved surfaces) extracted from their respective confocal microscopy images with a time lapse. The registration is based on non-rigid deformation of meshes created by user specified landmarks (parent cells and respective daughter cells). An algorithm is developed to triangulate the landmarks on the surface. The triangulation is then used to define cells’ location over time with the help of barycentric coordinates. The method uses local geometric coordinates to establish parent - daughter relationship between the cells on the two meshes. After the initial lineage assignment, neighbourhood relations are used to verify that the correct lineage was assigned. Cells which pass verification are then added to the triangulation and the process repeats. The method gave over 90 % accuracy for lineage tracking on a leaf sample of Arabidopsis thaliana, one of the largest dataset tested comprising 1411 cells

Signatures of spin-phonon coupling in hematite crystallites through dielectric and Raman spectroscopy

We report complex dielectric and Raman spectroscopy measurements in hematite crystallites, which are either hexagon-shaped plates or cuboids. Temperature variation of magnetization data in all these samples exhibits sharp Morin transition (TM). Moderate but clear enhancement in the real part of the dielectric constant $(\epsilon')$ is observed in the vicinity of the TM in all the samples. However a relaxation-like behavior in the imaginary part $(\epsilon'')$ is observed only in nanoplates or big cuboids across the TM. The real part of the dielectric constant fits well to the modified-Barrett equation above TM (in the spin-canted region), whereas clear deviations are observed below TM (in the pure antiferromagnetic region). The frequency of the phonon mode, deduced from the Barrett fitting, matches with the Eu Raman mode of hematite. Temperature-dependent Raman spectra reveal anomalies in all major phononic modes in the vicinity of the TM. Anharmonic fitting of the temperature-dependent Raman and modified-Barrett fitting of the dielectric data brings forward modifications in spin-phonon coupling in the vicinity of the Morin transition temperature in hematite