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Driven by environmental concerns and governmental directives, a sustained research effort in the last decade and half has led to the development of lead-free alternatives which can potentially replace the commercial lead-based piezoceramics in niche applications. Na 0.5 Bi 0.5 TiO 3 (NBT)-based lead-free piezoceramics have found acceptance as promising lead-free transducers in high power ultrasonic devices. An issue of concern however is the low depolarization temperature which limits the device's tolerance for temperature rise during operation. While several strategies have been reported to improve thermal depolarization in NBT-based piezoceramics, there is a lack of consensus regarding the most fundamental factor/mechanism which enhances the depolarization temperature. In this paper we unravel a coupled microstructural-structural mechanism which controls the thermal depolarization in NBT-based piezoceramics. First, we demonstrate the phenomenon of a considerable increase in the depolarization temperature, without significantly losing the piezoelectric property in unmodified NBT by increasing the grain size. We then establish a grain size controlled structural mechanism and demonstrate that the rise in depolarization temperature is primarily associated with the bigger grains allowing relatively large lattice distortion to develop in the poling stabilized long range ferroelectric phase. We reconfirmed the validity of this mechanism in the model morphotropic phase boundary (MPB) composition 0.94Na 0.5 Bi 0.5 TiO 3 -0.06BaTiO 3. For the sake of generalization, we demonstrate that the same mechanism is operative in another lead-based relaxor-ferroelectric system 0.62PbTiO 3 -0.38Bi(Ni 0.5 Hf 0.5)O 3. Our study provides the fundamental structural basis for understanding thermal depolarization delay in relaxor ferroelectric based piezoceramics. Image 1 [ABSTRACT FROM AUTHOR]

Abstract While studies in the past have shown that certain kinds of off-stoichiometry enhance the piezoelectric response of the lead-free piezoceramic Na 0.5 Bi 0.5 TiO 3 (NBT), there is a lack of clarity regarding the mechanism associated with this interesting phenomenon from the fundamental structural perspective. In this paper, we have investigated this issue comprehensively and succeeded in establishing a mutual correspondence between off-stoichiometry, grain size, crystal structure, dielectric and piezoelectric properties in Na 0.5 Bi 0.5 TiO 3 (NBT). Of the four different types of off-stoichiometric samples synthesized as per nominal formulae namely Na 0.5+x Bi 0.5 TiO 3 (Na-excess Na-series), Na 0.5-x Bi 0.5 TiO 3 (Na-deficient Na-series), Na 0.5 Bi 0.5+x TiO 3 (Bi-excess Bi-series), and Na 0.5 Bi 0.5-x TiO 3 (Bi-deficient Bi-series), the best piezoelectric response (d 33 ∼ 100 pC/N) was obtained in the Na-deficient series with x = 0.04. We succeeded in establishing the structural link between off-stoichiometry and piezoelectricity of this series by examining the structural state of the specimens in their poled state. We show that the off-stoichiometric compositions exhibiting higher piezoelectric response contain a higher fraction of the disordered ferroelectric phase coexisting with the field stabilized long-range ferroelectric (R3c) order. Beyond the critical off-stoichiometry (x > 0.04), the dominance of the structural disorder collapses the piezoelectric response of the system. We also show that what can be achieved by off-stoichiometry can as well be achieved by reducing the grain size of stoichiometric NBT. Our results suggest that the enhanced piezoelectric response of the off-stoichiometric compositions is due to their reduced grain size as compared to the stoichiometric composition, and that the nature of the defect species has a secondary role, if any. We found the same phenomenon/mechanism to be operative in the off-stoichiometric morphotropic phase boundary composition 0.94Na 0.5 Bi 0.5 TiO 3 -0.06BaTiO 3 (NBT-6BT). While our experiments confirm the role of the surviving structural heterogeneity (after poling) as an important contributing factor which enhances the piezoelectric response of NBT-based lead-free piezoceramics, we also use dielectric dispersion as a tool to show that the off-stoichiometric composition exhibiting highest piezoelectric response is characterized by maximum suppression of the disordered phase by the poling field. Graphical abstract Image 1 [ABSTRACT FROM AUTHOR]

Abstract Polycrystalline samples of Bi 0.9 Eu 0.1 FeO 3 , Bi 0.9 Gd 0.1 FeO 3 , and Bi 0.9 Eu 0.05 Gd 0.05 FeO 3 ceramics were synthesized by a solid-state reaction method, followed by rapid quenching to room temperature. Bi 0.9 Eu 0.1 FeO 3 shows higher magnetization than Bi 0.9 Gd 0.1 FeO 3 and Bi 0.9 Eu 0.05 Gd 0.05 FeO 3. This can be explained by lattice distortion, and the change in the statistical distribution of Fe3+/Fe2+. Similarly, ferroelectric polarization of Bi 0.9 Eu 0.1 FeO 3 was found to be higher than that of Bi 0.9 Gd 0.1 FeO 3 and Bi 0.9 Eu 0.05 Gd 0.05 FeO 3. However, the absolute value of the magnetocapacitance of Bi 0.9 Eu 0.05 Gd 0.05 FeO 3 (∼1.6%) was found to be higher than that of Bi 0.9 Eu 0.1 FeO 3 (∼1.3%) and Bi 0.9 Gd 0.1 FeO 3 (∼1.1%). In addition, the quadratic component of magnetoelectric coupling is higher for Bi 0.9 Eu 0.05 Gd 0.05 FeO 3 , which makes Bi 0.9 Eu 0.05 Gd 0.05 FeO 3 attractive for further study. Highlights • The dielectric constant at room temperature of sample-3 was found to be higher than that of samples-1 and 2. • The magnetization of sample-3 was found to be greater than that of samples-1 and 2. • The polarization–electric field loop of sample-3 was found to be better than that of samples-1 and 2. • The absolute value of the magnetocapacitance of sample-2 was found to be higher than that of sample s- 1 and 3. [ABSTRACT FROM AUTHOR]

We have investigated a series of compositions in the pseudo-ternary lead-free alloy system Na 1/2 Bi 1/2 TiO 3 -BaTiO 3 -BiFeO 3 with regard to its energy storage density and discharge efficiency. A composition 0.4(Na 0.5 Bi 0.5 TiO 3 )-0.225BaTiO 3 -0.375BiFeO 3 of this series was identified to give the best energy density and discharge efficiency. While conventional sintering gave energy density of 0.77 J/cm 3 and discharge efficiency of 67%, we achieved a remarkable increase in energy storage density (∼1.4 J/cm 3 ) and discharge efficiency (∼90%) by using spark plasma sintering of this composition. Our results suggest that this alloy system can be a potential lead-free candidate for high electric energy storage and discharge efficiency. [ABSTRACT FROM AUTHOR]

Background: Juvenile nasopharyngeal angiofibroma (JNA) has witnessed a four-fold increase in the incidence at our facility in the current decade as compared to the 1980s. With high global incidence of human pappilloma virus (HPV) related oropharyngeal cancer in India, we hypothesize its implication in JNA as it has not yet been reported.Methods: Clinico-Surgical variables of 6 patients of JNA were included for correlation and their tissue samples were subjected to western blotting (WB), polymerase chain reaction and immunoflorescence to demonstrate a definite association with HPV. In addition 6 control samples (adenoids) underwent WB analysis.Observations: A universal presence of HPV with JNA is novel 'discovery' and has suggested a possibility of a definite association. Only a single case suggested weak infection. None of the controls suggested infection, thus ruling out the presence of HPV in nasopharynx of normal population.Interpretation: With the dawn of this definite association, no specific conclusions can yet be drawn but a whole plethora of questions have emerged with our novel 'discovery'. [ABSTRACT FROM AUTHOR]

Background: An analysis of time distribution of juvenile nasopharyngeal angiofibroma (JNA) from the last 4 decades is presented.Methods: Sixty recurrences were analyzed as per actuarial survival. SPSS software was used to generate Kaplan-Meier (KM) curves and time distributions were compared by Log-rank, Breslow and Tarone-Ware test.Results: The overall recurrence rate was 17.59%. Majority underwent open transpalatal approach(es) without embolization. The probability of detecting a recurrence was 95% in first 24months and comparison of KM curves of 4 different time periods was not significant.Conclusion: This is the first and largest series to address the time-distribution. The required follow up period is 2years. Our recurrence is just half of the largest series (reported so far) suggesting the superiority of transpalatal techniques. The similarity of curves suggests less likelihood for recent technical advances to influence the recurrence that as per our hypothesis is more likely to reflect tumor biology per se. [ABSTRACT FROM AUTHOR]

Statement of problem: Obstructive sleep apnea (OSA) is a life-threatening condition that is diagnosed and evaluated primarily by polysomnography (PSG). The procedure is time consuming, expensive, and inconvenient for the patient, and may not be universally available. Purpose: The purpose of this pilot study was to evaluate posttreatment results on lateral cephalograms in patients with OSA. Material and methods: Lateral cephalograms of 16 patients diagnosed with OSA were made at the beginning of treatment and 4-6 weeks following treatment. Treatment modalities used in the study were the mandibular advancement device (MAD) and continuous positive airway pressure (CPAP) therapy (n=8). Pharyngeal dimensions, soft palate area and angle, and hyoid bone position were recorded for the comparisons. The data were analyzed using Student''s t test for the parametric analysis (α=.05). Results: A significant increase in the pharyngeal area (P<.001), a significant decrease in the soft palate area (P<.001), and vertical changes in the hyoid position were observed, with no significant change in the anteroposterior position of the hyoid bone. Conclusions: Within the limitations of this pilot study, lateral cephalograms were shown to be useful in evaluating treatment efficacy in subjects with OSA. (J Prosthet Dent 2010;103:170-177) [Copyright &y& Elsevier]

Na 0.5 Bi 0.5 TiO 3 (NBT) based lead-free piezoelectrics have received significant attention in the last few years for their anomalous high-field electrostrain response. The positional disorder on the nano/meso scale in these systems have a profound effect on their perceived global structure and dielectric properties. Here we have carried out a systematic analysis of the grain size dependent structural, ferroelectric, piezoelectric and high temperature electrical conduction behaviour of NBT. We show that the global monoclinic lattice distortion collapses even while the grains are unusually large (∼2.5 μm). We also found that the polarization switching ability and piezoelectric response of bulk NBT ceramics reduce drastically when grains are submicron in size. We use a powder poling technique to prove that the significant reduction of piezoelectricity in the submicron grain ceramic is not due to suppression of ferroelectricity within the grains itself, but rather due to inability of the grains to transform collectively to a long range rhombohedral ferroelectric state, either because of the clamping effect and/or enhanced incoherence of the grain boundaries. We also noted a qualitative change in the electrical conduction behaviour as a function of grain size and comment on a possible correlation between the grain size, global structure, piezoelectric response and oxygen ion conductivity of this lead-free compound. [ABSTRACT FROM AUTHOR]

The artemisinin resistance has posed a serious threat against malaria elimination lately. Past few years have seen important development of several peroxide based medicinal compounds and their derivatives such as trioxanes and tetraoxanes. Here, we report a rapid, one-pot method for synthesizing a new series of N -sulfonylpiperidine dispiro-1,2,4,5-tetraoxane analogs with diverse substitution on the tetraoxane ring i.e., various substituted alkyl and aryl sulfonyl chlorides, as well as cyclic, acyclic and aryl substituted ketones. All the synthesized tetraoxanes were characterized by spectroscopic (1H NMR,13C NMR), and spectrometric (High-resolution mass spectrometry) techniques and quantify by High Performance Liquid Chromatography (HPLC) analysis. The structure of compound 19 was confirmed by single crystal XRD. From the overall preliminary in vitro data, analogs 14, 16, 19, 20, 24, 41, and 44 exhibited potential IC 50 values in the nanomolar range between 4.7 ± 0.3 to 12.9 ± 1.1 nM against P. falciparum (Pf 3D7) strains of human malaria parasite. Furthermore, these selective analogs were evaluated in vivo for their antimalarial potential against P. berghei and results revealed that analogue 24 rapidly kills the infected cell at asexual erythrocytic stage, with activity comparable to positive control chloroquine. [Display omitted] • Synthesis ofg N -sulfonylpiperidine dispiro-1,2,4,5-tetraoxane analogs. • Compounds were characterized by various techniques such as 1H NMR, 13C NMR, HRMS (High-resolution mass Spectrometry) and single crystal X-ray diffraction (XRD) analysis. • Anti-plasmodial activities of the 41 analogs were evaluated against P. falciparum in vitro. • Selective analogs 14, 16, 19, 20, 24, 41 , and 44 were evaluated in vivo for their antimalarial potential against P. berghei and compound 24 exhibited the most potent fast killing antimalarial efficacy against asexual erythro-cytic stage. [ABSTRACT FROM AUTHOR]