Two-dimensional frustrated spin systems in high magnetic fields

We discuss our numerical results on the properties of the S = 1/2 frustrated J1-J2 Heisenberg model on a square lattice as a function of temperature and frustration angle phi = atan(J2/J1) in an applied magnetic field. We cover the full phase diagram of the model in the range -pi <= phi <= pi. The discussion includes the parameter dependence of the saturation field itself, and addresses the instabilities associated with it. We also discuss the magnetocaloric effect of the model and show how it can be used to uniquely determine the effective interaction constants of the compounds which were investigated experimentally.Comment: 4 pages, 5 figures, proceedings of RHMF 200

Giant nonlinear conduction and thyristor-like negative derivative resistance in BaIrO3 single crystals

We synthesized single-crystalline samples of monoclinic BaIrO3 using a molten flux method, and measured their magnetization, resistivity, Seebeck coefficient and nonlinear voltage-current characteristics. The magnetization rapidly increases below a ferromagnetic transition temperature TC of 180 K, where the resistivity concomitantly shows a hump-type anomaly, followed by a sharp increase below 30 K. The Seebeck coefficient suddenly increases below TC, and shows linear temperature dependence below 50 K. A most striking feature of this compound is that the anomalously giant nonlinear conduction is observed below 30 K, where a small current density of 20 A/cm2 dramatically suppresses the sharp increase in resistivity to induce a metallic conduction down to 4 K.Comment: 10 pages, 4 figures Submitted to Physical Review Letter

Techniques of deep learning and image processing in plant leaf disease detection: a review

Computer vision techniques are an emerging trend today. Digital image processing is gaining popularity because of the significant upsurge in the usage of digital images over the internet. Digital image processing is a practice that can help in designing sophisticated high-end machines, which can hold the ophthalmic functionality of the human eye. In agriculture, leaf examination is important for disease identification and fair warning for any deficiency within the plant. Many prominent plant species are facing extinction because of a lack of knowledge. A proper realization of computer vision techniques aid in extracting a significant amount of information from leaf image. This necessitates the requirement of an automatic leaf disease detection method to diagnose disease occurrences and severity, for timely crop management, by spraying pesticides. This study focuses on techniques of digital image processing and machine learning rendered in plant leaf disease detection, which has great potential in precision agriculture. To support this study, techniques exercised by various researchers in recent years are tabulated

Acute Toxicity and Vascular Properties of Seed of Parkia Biglobosa (Jacq) R. Br Gift (Mimosaceae) on Rat Aorta

The authors report here the results of study on Parkia biglobosa seeds used in Burkina Faso for arterial hypertension treatment. Investigations were done on acute toxicity and vascular properties of fermented and roasted seeds. Acute toxicity test using mice, revealed by the intraperitoneal route a lethal dose 50 (LD50) of 1800 mg/kg and 1600 mg/kg of body weight for aqueous extract from roasted and fermented seeds respectively. According to the scale of Hodge and Sterner and that of the World Health Organization, such drugs would be classified lightly toxic. Oral administration (up to 3000 mg/kg) did not induce any death of animal. For the vascular properties, the effects of these products were tested on the aorta isolated from rats. The cumulative administration of extract from roasted and fermented seeds (0.1-10 mg/mL) in an organ bath induced a concentration-dependent relaxation of the aorta pre contracted by phenylephrine, with or without functional endothelium. The extracts (10 mg/mL) inhibited for 100% the contraction induced by phenylephrine. The EC50 values in presence and absence of endothelium were respectively of 5.37 &plusmn; 0.12 and 4.19 &plusmn; 1.02 mg/mL for fermented seeds; for roasted seeds these values were respectively, 5.39 &plusmn; 1.12 and 5.93 &plusmn; 0.95 mg/mL. Nevertheless, low concentration of roasted seeds (1-4 mg/mL) induced endothelium-dependent relaxation and this effect was inhibited by indomethacin (10-5M), and not by L-NAME (310-4M). These experimental results revealed a vasorelaxant effect of P. biglobosa seeds. P. biglobosa seems to act directly on the smooth muscle and via endothelium involving the generation of vasodilatating prostaglandins. This vasodilator effect would be in favor of an anti hypertensive property of P. biglobosa seeds.Key words: Acute toxicity; vasodilator; endothelium; Parkia biglobosa

Genetic and Neuroanatomical Support for Functional Brain Network Dynamics in Epilepsy

Focal epilepsy is a devastating neurological disorder that affects an overwhelming number of patients worldwide, many of whom prove resistant to medication. The efficacy of current innovative technologies for the treatment of these patients has been stalled by the lack of accurate and effective methods to fuse multimodal neuroimaging data to map anatomical targets driving seizure dynamics. Here we propose a parsimonious model that explains how large-scale anatomical networks and shared genetic constraints shape inter-regional communication in focal epilepsy. In extensive ECoG recordings acquired from a group of patients with medically refractory focal-onset epilepsy, we find that ictal and preictal functional brain network dynamics can be accurately predicted from features of brain anatomy and geometry, patterns of white matter connectivity, and constraints complicit in patterns of gene coexpression, all of which are conserved across healthy adult populations. Moreover, we uncover evidence that markers of non-conserved architecture, potentially driven by idiosyncratic pathology of single subjects, are most prevalent in high frequency ictal dynamics and low frequency preictal dynamics. Finally, we find that ictal dynamics are better predicted by white matter features and more poorly predicted by geometry and genetic constraints than preictal dynamics, suggesting that the functional brain network dynamics manifest in seizures rely on - and may directly propagate along - underlying white matter structure that is largely conserved across humans. Broadly, our work offers insights into the generic architectural principles of the human brain that impact seizure dynamics, and could be extended to further our understanding, models, and predictions of subject-level pathology and response to intervention

HPLC Method for Determination of p-coumaric acid from the Medicinal Herb Leptadinia reticulata

The aim of present study was to develop and validate a simple, precise and rapid HPLC method for the quantification of p-coumaric acid in Leptadinia reticulata extractst. The analysis was performed by reverse-phase chromatography on an phenomenex C18 columns with isocratic elution of Methanol and 0.8%-Formic acid in water (6:4) at a flow rate of 1.0mL/min, a column temperature of 35°C, photodiode array detector detection at 326 nm. The method validated in terms of linearity accuracy precision LOD, LOQ and stability. The herb Leptidinia reticulata contains 0.17% p-coumaric acid. The linear range of method was 0.25-50µg/ml with correlation coefficient of 0.9993, the recovery was 98-99.4% and the relative standard deviation is 0.98 % (n=6). The developed method was found to be a relatively simple, precise and reproducible for the quantification of p-coumaric acid. The method does not employ any derivatization procedure and can be used as a quality control tool for the routine analysis of    p-coumaric acid from an herb Leptadinia reticulata

Two- and three-dimensional magnetic correlations in the spin-1/2 square-lattice system Zn2VO(PO4)2

The magnetic correlations in the quasi-two dimensional spin-1/2 square-lattice system Zn2VO(PO4)2 have been investigated by neutron diffraction technique. A long-range antiferromagnetic (AFM) ordering below 3.75 K (TN) has been observed with a reduced moment of 0.66(2) {\mu}B per V ion at 1.5 K. In a given ab plane, the AFM spin arrangement is N\'eel type and the AFM layers are coupled ferromagnetically along the c axis. Remarkably, we have observed a pure 2D short-range AFM ordering in the ab plane above TN. Interestingly, the coexistence of diffuse magnetic scattering and three dimensional antiferromagnetic Bragg peaks has been found below TN, indicating the presence of spin-waves as confirmed by our calculation using the linear spin-wave theory. The observed results are discussed in the light of existing theory for a two-dimensional spin-1/2 square-lattice system.Comment: 19 PAGES, 8 FIGURES, Accepted for publication in Physical Review B 201