Ferroelectric Phase Transitions in Films with Depletion Charge

We consider ferroelectric phase transitions in both short-circuited and biased ferroelectric-semiconductor films with a space (depletion) charge which leads to some unusual behavior. It is shown that in the presence of the charge the polarization separates into `switchable' and `non-switchable' parts. The electric field, appearing due to the space charge, does not wash out the phase transition, which remains second order but takes place at somewhat reduced temperature. At the same time, it leads to a suppression of the ferroelectricity in a near-electrode layer. This conclusion is valid for materials with both second and first order phase transitions in pure bulk samples. Influence of the depletion charge on thermodynamic coercive field reduces mainly to the lowering of the phase transition temperature, and its effect is negligible. The depletion charge can, however, facilitate an appearance of the domain structure which would be detrimental for device performance (fatigue). We discuss some issues of conceptual character, which are generally known but were overlooked in previous works. The present results have general implications for small systems with depletion charge.Comment: 11 pages, REVTeX 3.1, five eps-figures included in the text. Minor clarifications in the text. To appear in Phys. Rev. B 61, Apr 1 (2000

Customer emotions in service failure and recovery encounters

Emotions play a significant role in the workplace, and considerable attention has been given to the study of employee emotions. Customers also play a central function in organizations, but much less is known about customer emotions. This chapter reviews the growing literature on customer emotions in employee–customer interfaces with a focus on service failure and recovery encounters, where emotions are heightened. It highlights emerging themes and key findings, addresses the measurement, modeling, and management of customer emotions, and identifies future research streams. Attention is given to emotional contagion, relationships between affective and cognitive processes, customer anger, customer rage, and individual differences

Large expert-curated database for benchmarking document similarity detection in biomedical literature search

Document recommendation systems for locating relevant literature have mostly relied on methods developed a decade ago. This is largely due to the lack of a large offline gold-standard benchmark of relevant documents that cover a variety of research fields such that newly developed literature search techniques can be compared, improved and translated into practice. To overcome this bottleneck, we have established the RElevant LIterature SearcH consortium consisting of more than 1500 scientists from 84 countries, who have collectively annotated the relevance of over 180 000 PubMed-listed articles with regard to their respective seed (input) article/s. The majority of annotations were contributed by highly experienced, original authors of the seed articles. The collected data cover 76% of all unique PubMed Medical Subject Headings descriptors. No systematic biases were observed across different experience levels, research fields or time spent on annotations. More importantly, annotations of the same document pairs contributed by different scientists were highly concordant. We further show that the three representative baseline methods used to generate recommended articles for evaluation (Okapi Best Matching 25, Term Frequency-Inverse Document Frequency and PubMed Related Articles) had similar overall performances. Additionally, we found that these methods each tend to produce distinct collections of recommended articles, suggesting that a hybrid method may be required to completely capture all relevant articles. The established database server located at https://relishdb.ict.griffith.edu.au is freely available for the downloading of annotation data and the blind testing of new methods. We expect that this benchmark will be useful for stimulating the development of new powerful techniques for title and title/abstract-based search engines for relevant articles in biomedical research.Peer reviewe

Influence of Temperature on Reducing Gas Sensing Performance of Nanocrystalline Zinc Ferrite

Pure phase, zinc ferrite (ZnFe2O4) nanoparticles were synthesized at lower temperature (80 °C) by auto combustion synthesis method. The resulting ‘as synthesized’ powder was heat treated (HT) at 560 °C for 2 h in air atmosphere. As-synthesized particles had sizes ~10 nm with spherical shape. Further, these spherically shaped nanoparticles tended to change their morphology to hexagonal plate shape with increasing HT temperature. The band gap of the ‘as synthesized’ and HT zinc ferite, as determined by using UV–Vis spectroscopy were found to be 1.92 and 1.86 eV respectively. Gas responses of the ZnFe2O4 nanoparticles were measured by exposing them to ethanol gas vapors. It was found that the zinc ferrite nanoparticles exhibited various sensing responses to ethanol gas at different operating temperature. The best sensitivity was observed at low temperature for ‘as synthesized’ ferrite nanoparticles than HT zinc ferrite nanoparticles. Sensing material that had smaller particle size and larger specific surface area was observed to have larger gas sensitivity and vice-versa

HEPATOPROTECTIVE AND ANTIOXIDANT ACTIVITY OF ALPINIA MALACCENSIS ROSCOE RHIZOME

Objective: The present study aims to evaluate hepatoprotective activity, antioxidant activity and total phenolic content of methanolic extract from rhizomes of A. malaccensis.Methods: The hepatoprotective activity in mice was studied by inducing oral dose at 250 mg/kg and 500 mg/kg b. wt., antioxidant activity was evaluated by different method viz; the superoxide anion scavenging activity, hydroxyl radical scavenging activity, nitric oxide scavenging activity, DPPH radical scavenging activity and total phenolic content.Results: The mice were significantly re established from hepatotoxicity evident by analyzing the factors such as triglycerides, ALT, AST, glucose, cholesterol, total protein, bilirubin, albumin and urea levels. Further more histopathological results revealed the significant improvement of liver. Methanolic extracts of rhizomes of A. malaccensis showed abilities to scavenge hydroxyl, superoxide free radicals, nitric oxide, DPPH with IC50 values of 50.42, 71.19, 96.38, 61.46 µg/ml and reducing power ability with the RP50 value of 183.54 µg/ml. The methanolic extract was found to have a total phenolic content of 48.18 µg/ml.Conclusion: Our study reveals the therapeutic effect of A. malaccensis on treated mice as well as the strong antioxidant potential with its total phenolic content. A. malaccensis so may be used as herbal medicine to replace synthetic one.Â

Transcranial Doppler: Techniques and advanced applications: Part 2

10.4103/0972-2327.173407Annals of Indian Academy of Neurology191102-10