Linear and Nonlinear Optical Properties of Graphene Quantum Dots: A Computational Study

Due to the advantage of tunability via size, shape, doping and relatively low level of loss and high extent of spatial confinement, graphene quantum dots (GQDs) are emerging as an effective way to control light by molecular engineering. The collective excitation in GQDs shows both high energy plasmon frequency along with frequencies in the terahertz (THz) region making these systems powerful materials for photonic technologies. Here, we report a systematic study of the linear and nonlinear optical properties of large varieties of GQDs (400 systems) in size and topology utilizing the strengths of both semiempirical and first-principles methods. Our detailed study shows how the spectral shift and trends in the optical nonlinearity of GQDs depends on their structure, size and shape. Among the circular, triangular, stripe, and random shaped GQDs, we find that GQDs with inequivalent sublattice atoms always possess lower HOMO-LUMO gap, broadband absorption and high nonlinear optical coefficients. Also, we find that for majority of the GQDs with interesting linear and nonlinear optical properties have zigzag edges, although reverse is not always true. We strongly believe that our findings can act as guidelines to design GQDs in optical parametric oscillators, higher harmonic generators and optical modulators.Comment: 21 pages, 11 figures, 4 table

Designing Transferable Skills Inventory for Assessing Students using Group Discussion: A Case Study of First Year Electrical and Electronics Engineering Students

Employability skills among engineering graduates have been a concern due to their inability to perform on a professional platform to the employer’s expected level.  As they are higher cognitive skills, they are to be nurtured during the graduation period.  Keeping this in view, group discussions are identified as one of the methods to elicit leadership, problem solving and communication skills among the student community.  The present study also gives importance to peer assessment as a part of collaborative learning. Keywords:  Transferable skills, group discussion, employability skills, problem solving and conceptualizatio

Studies on Potential Pesticides-Part XIV : Synthesis and Biological Activities of some new Thiosemicarbazide and Triazole Derivatives

Some new N-[5-(substituted phenoxymethyl)-1,3,4-oxadiazoly1-2-thioacetyl]-N-aryl-thiosemicarbazides have been synthesised by the condensation of appropriate hydrazine with aryliosothiocyanates. Cyclisation of these thiosemicarbazides in alkaline medium gives 3-[5-(substituted phenoxymethyl)-1,3,4-oxadiazolyl-2-thioacetyl]-4-aryl-5-mercapto-1,2,4-triazoles. All these compounds have been evaluated for their antibacterial properties and some of these have been screened for their anti fungal activity and AChE inhibition

FORMULATION DEVELOPMENT AND EVALUATION OF GASTRO-RETENTIVE DOSAGE FORM OF ATAZANAVIR SULPHATE

Objective: To improve dissolution properties of atazanavir sulphate by preparing gastro-retentive granules by solid dispersion method and development of RP-HPLC method for estimation of this drug.Methods: Estimation of atazanavir sulphate was done using high performance liquid chromatography (HPLC) on inertsil column (5 µm, 250x4, 6 mm) with a mobile phase consists of methanol: water (91:9 v/v), at 0.5 ml/min flow rate and 249 nm UV detection. The method was validated as per ICH guidelines. Selection of the carrier for gastro-retentive formulation was based on phase solubility study of the drug. Solid dispersions of gastro-retentive granules of different composition of drug and carrier, were prepared by the kneading, heating and solvent evaporation. A 32factorial design was applied to optimize the gastro-retentive formulation. The amounts of polyethylene glycol 6000 (PEG 6000) (X1) and hydroxypropyl methyl cellulose (HPMC) (X2) were selected as independent variables and in vitro-release at 5, 9 h and total floating time was selected as dependent variables. Results: HPLC method was found to be linear in a concentration range of 10-60 μg/ml of the drug (r2= 0.999). The low value of % RSD in precision study indicates reproducibility of the method. The low value of LOD and LOQ suggests the sensitivity of the method. The solubility enhancement study of drug with various carriers followed descending order of solubility [Gelucire 44/14>PEG 6000>polyvinyl pyrrilidone (PVP)]. Highest % cumulative release was observed for the heating method at drug polymer (PEG 6000) ratio 1:5. Hence, this ratio has been selected for preparation of solid dispersion. From comparison of dissolution profile of formulated batches, formulation F4 [containing PEG6000 (1.6 g) and HPMC (200 mg)] showed promising dissolution parameters with desired floating properties.Conclusion: Results obtained by validation studies suggested that the developed HPLC method is simple, accurate, precise and can be used for routine analysis of atazanavir sulphate formulation. Results of evaluation of prepared batches indicate that batch F4 is a promising formulation for gastro-retentive dosage form of drug.Â

FORMULATION ANDCHARACTERIZATION OF OLANZEPINELOADED MUCOADHESIVE MICROSPHERES

Objective: The objective of this research was to formulate and evaluate olanzapine (OLE) mucoadhesive microsphere prepared using carbopol and sodium combination. OLE having extensive hepatic first pass metabolism and low bioavailability problem, determined the need for the development of sustained release formulation.Methods: OLE mucoadhesive microspheres were prepared by ionic gelation method. OLE mucoadhesive microspheres were prepared by ionic gelation method by using calcium chloride as crosslinking agent. The OLE mucoadhesive microsphere was characterized by particle size measurement, process yield, morphology of microsphere, drug entrapment efficiency, mucoadhesion test, differential scanning calorimetry, powder X-ray diffraction, Fourier transforms infrared (FTIR) study and in-vitro drug release.Results: The OLE mucoadhesive microsphere having mean particle size ranged from 546.0 µm to 554.3 µm, and the entrapment efficiencies ranged from 73% to 96%. All the olanzapine (OLE) microsphere batches showed good in-vitro mucoadhesive property ranging from 75.89% to 96.47% and in the in-vitro wash off test ranging from 68.12% to 81.3%. FTIR studies indicated the no drug-polymer interactions in the ideal formulation F9. Therewere no compatibility issues, and the crystallinity of OLE was found to be reduced shoeing less intense peak in prepared mucoadhesive microspheres, which were confirmed by differential scanning calorimeter and X-ray diffraction studies. Among different formulations, the OLE microspheres of batch F9 had shown the optimum percent drug entrapment of microspheres. Release pattern of OLE from F9 microspheres batch followed Higuchi kinetic model. Stability studies were carried out for F9 formulation at 4°C/ambient, 25±2°C/60±5%, 40±2°C/75±5% relative humidity revealed that the drug entrapment, mucoadhesive behavior, and drug release were within permissible limits.Conclusion: The results obtained in this work demonstrate the use of carbopol and sodium alginate polymer for preparation of mucoadhesive microsphere.Keywords: Ionic gelation method, Gastroretentive delivery, Mucoadhesive microsphere, Carbopol

Preparation and Investigation of Suitability of Gadolinium Oxide Nanoparticle Doped Polyvinyl Alcohol Films for Optoelectronic Applications

Gd2O3 nanoparticles synthesized by solution combustion method were used to prepare PVA-Gd2O3 nanocomposite films of varying concentrations (2 wt%–6 wt% of filler) by solution casting method. Being a rare earth oxide, gadolinium oxide was expected to exhibit good photoluminescence and the nanocomposite was expected to be flexible as well. The Gd2O3 nanoparticles prepared were found to be in cubic phase with an average size of 19 nm. Raman spectra showed the incorporation of Gd2O3 into the polymer matrix. Scanning electron microscope images revealed that the particles were porous in nature, agglomerated and distributed evenly on the surface of the film in the form of clusters. The UV–Visible absorption spectra gave direct optical energy band gap value in the range 5.78–4.86 eV. Both band gap as well as the Urbach energy are seen to decrease with increasing concentration of the dopant. Four prominent photoluminescence peaks were observed in all the three composite films in the UV region (318 nm), deep blue region (396 nm), blue region (477 nm) and green region (553 nm). The color purity of the films using CIE coordinates was found to be the highest, 82.81%, in the 2 wt% film making this film a promising material for blue OLED's and blue flexible screen

Drugs in pregnancy and lactation

Drug use during pregnancy and lactation is an almost inevitable event. Some of the drugs may have adverse effects on the baby on exposure. It is therefore necessary for the physician to be aware of the changes in pharmacokinetics and pharmacodynamics during pregnancy. Knowledge about the known teratogens and drugs safe to be used during pregnancy is essential on the part of the prescribing physician. There are many factors affecting drug passage into the milk and thus affecting the child in some cases. There are also some drugs affecting lactation. All this data needs to be carefully studied by the physician