7,439 research outputs found
Spin-lattice coupling mediated giant magnetodielectricity across the spin reorientation in Ca2FeCoO5
The structural, phonon, magnetic, dielectric, and magneto dielectric
responses of the pure bulk Brownmillerite compound Ca2FeCoO5 are reported. This
compound showed giant magneto dielectric response (10%-24%) induced by strong
spin-lattice coupling across its spin reorientation transition (150-250 K). The
role of two Debye temperatures pertaining to differently coordinated sites in
the dielectric relaxations is established. The positive giant
magneto-dielectricity is shown to be a direct consequence of the modulations in
the lattice degrees of freedom through applied external field across the spin
reorientation transition. Our study illustrates novel control of
magneto-dielectricity by tuning the spin reorientation transition in a material
that possess strong spin lattice coupling.Comment: 7 pages, 12 figure
Comparison of metabolic effects of glimepride and sitagliptin with metformin in patients suffering from type 2 diabetes mellitus in a tertiary care hospital
Background: Diabetes mellitus (DM) is one of the major causes of mortality & morbidity, and patient’s with better control of glycaemic parameters have lesser chronic complications associated with it. Though monotherapy with metformin is first choice for T2DM but is effective in less than 50% of patient and they should be managed with two drug therapy. Both Glimepiride and Sitagliptin are effective with metformin but there has been no study done in this region hence, we planned to study comparison of effects of glimepiride and sitagliptin with metformin in patient of T2DM.Methods: This prospective, open-label, randomized study was done in all patient diagnosed with T2DM, not adequately managed by metformin alone. The patient was divided into two group G (Glimepiride with Metformin) and Group S (Sitagliptin with Metformin) and had a follow up at 3 and 6 months. The biochemical parameters were assessed at 12 weeks and 24 weeks.Results: The result of this study show that both glimepiride and sitagliptin with metformin significantly (p<0.05) lowered both the fasting blood sugar as well as postprandial blood glucose at 3 and 6 months. Glimepiride was more effective in lowering (p<0.05) the plasma glucose at 3 months but both the drugs had comparable result at 6 months. This study also showed that glycosylated haemoglobin was lowered in both groups at three and six months as compared to Day 0 (p<0.05), with glimepiride having better control of glycosylated haemoglobin at 3 months with both groups having comparable result at 6 months.Conclusions: To conclude, this study compared effects of sitagliptin and glimepiride on glycaemic parameters in patients of T2DM and found that both drugs had comparable results
Self-propulsion in 2D Confinement: Phoretic and Hydrodynamic Interactions
Chemically active Janus particles generate tangential concentration gradients
along their surface for self-propulsion. Although this is well studied in
unbounded domains, the analysis in biologically relevant environments such as
confinements is scarce. In this work, we study the motion of a Janus sphere in
weak confinement. The particle is placed at an arbitrary location, with an
arbitrary orientation between the two walls. Using the method of reflections,
we study the effect of confining planar boundaries on the phoretic and
hydrodynamic interactions, and their consequence on the Janus particle
dynamics. The dynamical trajectories are analyzed using phase diagrams for
different surface coverage of activity and solute-particle interactions. In
addition to near wall states such as `sliding' and `hovering', we demonstrate
that accounting for two planar boundaries reveals two new states:
channel-spanning oscillations and damped oscillations around the centerline,
which were characterized as `scattering' or `reflection' by earlier analyses on
single-wall interactions. Using phase diagrams, we highlight the differences in
inert-facing and active-facing Janus particles. We also compare the dynamics of
Janus particles with squirmers for contrasting the chemical interactions with
hydrodynamic effects. Insights from the current work suggest that biological
and artificial swimmers sense their surroundings through long-ranged
interactions, that can be modified by altering the surface properties.Comment: To appear in European Physical Journal
Composition and Structure Based GGA Bandgap Prediction Using Machine Learning Approach
This study focuses on developing precise machine learning (ML) regression
models for predicting energy bandgap values based on chemical compositions and
crystal structures. The primary aim is to match the accuracy of predictions
derived from GGA-PBE calculations and validate them through density functional
theory (DFT)-based band structure calculations. We assessed eight standalone ML
regression models, including AdaBoost, Bagging, CatBoost, LGBM, RF, DT, GB, and
XGB. These models were analyzed for their ability to predict GGA-PBE bandgap
values across diverse material structures and compositions, using a dataset
containing bandgap values for 106,113 compounds. Additionally, we constructed
four ensemble models using the stacking method and seven using the bagging
method. These ensemble models incorporated RidgeCV and LassoCV to explore if
ensemble techniques could enhance prediction accuracy. The dataset was divided
into subsets of varying sizes: 10,000, 25,000, 50,000, and 100,000 entries. We
determined feature importance through permutation techniques and established a
correlation coefficient matrix using the Pearson correlation method. The Random
Forest (RF) model emerged as the top performer among standalone models,
achieving an R2 value of 0.943 and an RMSE value of 0.504 eV. Bagging
regression demonstrated improved performance across different dataset sizes
with streamlined feature selection. Ensemble models, particularly bagging,
consistently outperformed standalone models, achieving the best R2 value of
0.948 and an RMSE value of 0.479 eV in the test dataset. Using the
best-performing model, we predicted bandgap values for new half-Heusler
compounds with 18 valence electron counts. These predictions were successfully
validated using accurate DFT calculations. DFT calculations indicated that the
newly predicted compounds are narrow bandgap semiconductors with dynamic
stability.Comment: 17 pages, 17 figures, Research pape
Accelerating Discovery of Vacancy Ordered 18-Valence Electron Half-Heusler Compounds: A Synergistic Approach of Machine Learning and Density Functional Theory
In this study, we attempted to model vacancy ordered half Heusler compounds
with 18 valence electron count (VHH) derived from 19 VEC compounds such as
TiNiSb such that the compositions will be Ti0.75NiSb, Zr0.75NiSb and Hf0.75NiSb
with semiconducting behavior. The main motivation is that such a
vacancy-ordered phase not only introduces semi conductivity but also it
disrupts the phonon conducting path in HH alloys and thus reduces the thermal
conductivity and as a consequence enhances the thermoelectric figure of merit.
In order to predict the formation energy ({\Delta}Hf) from composition and
crystal structure we have used 4684 compounds for their {\Delta}Hf values are
available in the material project database and trained a machine learning model
with R2 value of 0.943. Using this trained model, we have predicted the
{\Delta}Hf of a list of VHH. From the predicted database of VHH we have
selected Zr0.75NiSb and Hf0.75NiSb to validate the machine learning prediction
using accurate DFT calculation. The calculated {\Delta}Hf for these two
compounds from DFT calculation are found to be comparable with our ML
prediction. The calculated electronic and lattice dynamics properties show that
these materials are narrow band gap semiconductors and are dynamically stable
as their all-phonon dispersion curves are having positive frequencies. The
calculated Seebeck coefficient, electrical conductivity as well as thermal
conductivity, power factor and thermoelectric figure of merit are analyzed.Comment: 5 pages, 2 figures, conferenc
- …