Effect of Eu3+ doping on structural and optical properties of zirconium titanate

The Europium activated (1-9 mol %) Zirconium Titanate nanoparticles (NPs) have been synthesized by the green solution combustion method using Aloe Vera gel extract as a reducing agent, followed by the calcination at 720 °C for 3hrs. All the synthesized samples crystallize in a pure orthorhombic crystal structure with the space group of Pbcn. The surface and bulk morphology were analyzed. The crystallite size increases, whereas the direct energy band gap was found to decrease with an increase in dopant concentration. Further, the effect of dopant concentration on the photoluminescence properties was studied. The presence of Eu³⁺ ion in the trivalent state in the host lattice was confirmed by its characteristic emission at 610 nm due to ⁵D₀→⁷F₂ (λ_ex = 464 nm). The CIE coordinates were found in the red region of the CIE 1931 diagram. The CCT coordinates lie in the range 6288-7125 K. The Judd-Ofelt parameters and derived quantities were analyzed. This theory confirms the high symmetry of Eu³⁺ ions in the host lattice. These findings imply that ZTO:Eu³⁺ can be employed as a nanopowder material in a red-emitting phosphor material.

Comparative studies of energy saving polymers and fabrication of high performance transparent polymer by solvent bonding

This work investigates the possibility of using polyetherimide (PEI) as an energy saving alternative to glass, polymethylmethacrylate (PMMA) and polycarbonate (PC) by carrying out heat transfer analysis and suggests vaporized solvent bonding as a viable bonding technique for the fabrication of PEI. By heat transfer analysis using building energy simulation, it is observed that less energy is expended for space-conditioning of a building with windows made of PEI when compared to glass, PMMA and PC. The compression moulding technique is used to mould PEI and fabrication is done using a solvent mixture of dimethyl sulfoxide and tetrahydrofuran in 1:1 ratio. The optical properties of the bonded specimen are studied using UV-visible spectrophotometry and it is found that PEI does not allow UV wavelength radiation to pass through while transmitting visible wavelengths. The mechanical strength of the bond is tested using lap shear tensile strength test and the type of failure is observed to be cohesive from the structure. This is indicative of the fact that using this particular solvent to bond PEI results in the maximum possible strength.

Experimental investigation on preconditioned rate induced tipping in a thermoacoustic system

Many systems found in nature are susceptible to tipping, where they can shift from one stable dynamical state to another. This shift in dynamics can be unfavorable in systems found in various fields ranging from ecology to finance. Hence, it is important to identify the factors that can lead to tipping in a physical system. Tipping can mainly be brought about by a change in parameter or due to the influence of external fluctuations. Further, the rate at which the parameter is varied also determines the final state that the system attains. Here, we show preconditioned rate induced tipping in experiments and in a theoretical model of a thermoacoustic system. We provide a specific initial condition (preconditioning) and vary the parameter at a rate higher than a critical rate to observe tipping. We find that the critical rate is a function of the initial condition. Our study is highly relevant because the parameters that dictate the asymptotic behavior of many physical systems are temporally dynamic.

A hybrid Factored Frontier algorithm for Dynamic Bayesian Networks with a biopathways application

Dynamic Bayesian Networks (DBNs) can serve as succinct probabilistic dynamic models of biochemical networks. To analyze these models, one must compute the probability distribution over system states at a given time point. Doing this exactly is infeasible for large models; hence one must use approximate algorithms. The Factored Frontier algorithm (FF) is one such algorithm. However FF as well as the earlier Boyen-Koller (BK) algorithm can incur large errors. To address this, we present a new approximate algorithm called the Hybrid Factored Frontier (HFF) algorithm. At each time slice, in addition to maintaining probability distributions over local states-as FF does-HFF explicitly maintains the probabilities of a number of global states called spikes. When the number of spikes is 0, we get FF and with all global states as spikes, we get the exact inference algorithm. We show that by increasing the number of spikes one can reduce errors while the additional computational effort required is only quadratic in the number of spikes. We validated the performance of HFF on large DBN models of biopathways. Each pathway has more than 30 species and the corresponding DBN has more than 3,000 nodes. Comparisons with FF and BK show that HFF is a useful and powerful approximate inferencing algorithm for DBNs.

The utility of second look microlaryngoscopy after trans oral laser resection of laryngeal cancer

In the past few decades more and more number of tumors of the glottis and supraglottis are been treated with single stage transoral laser microsurgery (TOLS). TOLS for the treatment of glottic and supraglottic carcinoma with anterior commissure (A-com) and/paraglottic space involvement is associated with a high rate of recurrence. We prospectively evaluated the outcomes of laser microsurgery and the impact of second look operation in these patients. Twenty-three patients with glottic and supraglottic carcinoma underwent transoral laser micro resection of the lesions. Subsequently five patients underwent second look microlaryngeal evaluation 6-8 months later for non-satisfactory healing, poor voice, and or suspicion of recurrent disease. Patients with A-com involvement and or paraglottic space involvement were followed up longitudinally for the effectiveness and timing of second look microsurgery. After initial transoral laser micro resection, all patients achieved microscopically clear resection margins. At second look microlaryngeal evaluation, local recurrence was found in four of 23 patients. Of these, two patients were salvaged by second look surgery and are disease free, whereas in two others, the larynx had to be subjected to open surgical intervention. One of two had extensive local recurrent tumor and underwent total laryngectomy with neck dissection followed by post-operative radiotherapy. Tracheohyoidopexy was done with successful functional and oncologic outcome for another patient who had local recurrence for the third time. Only the patient who underwent total laryngectomy with neck dissection was subjected to adjuvant post-operative radiotherapy. Finally, larynx was saved in 21 out of 23 patients.

A genetic model to investigate drug-target interactions at the ribosomal decoding site

Recent advances in X-ray crystallography have greatly contributed to the understanding of the structural interactions between aminoglycosides and the ribosomal decoding site. Efforts to genetically probe the functional relevance of proposed drug-nucleotide contacts have in part been hampered by the presence of multiple rRNA operons in most bacteria. A derivative of the Gram-positive Mycobacterium smegmatis was rendered single rRNA operon allelic by means of gene inactivation techniques. In this system, genetic manipulation of the single chromosomal rRNA operon results in cells carrying homogeneous populations of mutant ribosomes. An exhaustive mutagenesis study of the ribosomal A site has been performed to define the importance of individual drug-nucleotide contacts. Mutational alterations in the M. smegmatis decoding site are discussed here, comparing the results with those obtained in other organisms. Implications for the selectivity of antimicrobial agents and for the fitness cost of resistance mutations are addressed.