WorldWideScience

Sample records for aln mole fraction

  1. psychrometry: from partial pressures to mole fractions

    African Journals Online (AJOL)

    ES Obe

    1980-03-01

    Mar 1, 1980 ... ABSTRACT. This study uses the viria1 and interaction coefficients of the normal air components in deriving compressibility factors and thereafter a simple iterative formulation for mole fractions. Conversion from partial pressures to mole fractions now becomes tractable by means of determinate multipliers.

  2. Microwave Determination of Water Mole Fraction in Humid Gas Mixtures

    Science.gov (United States)

    Cuccaro, R.; Gavioso, R. M.; Benedetto, G.; Madonna Ripa, D.; Fernicola, V.; Guianvarc'h, C.

    2012-09-01

    A small volume (65 cm3) gold-plated quasi-spherical microwave resonator has been used to measure the water vapor mole fraction x w of H2O/N2 and H2O/air mixtures. This experimental technique exploits the high precision achievable in the determination of the cavity microwave resonance frequencies and is particularly sensitive to the presence of small concentrations of water vapor as a result of the high polarizability of this substance. The mixtures were prepared using the INRIM standard humidity generator for frost-point temperatures T fp in the range between 241 K and 270 K and a commercial two-pressure humidity generator operated at a dew-point temperature between 272 K and 291 K. The experimental measurements compare favorably with the calculated molar fractions of the mixture supplied by the humidity generators, showing a normalized error lower than 0.8.

  3. Raman line imaging for spatially and temporally resolved mole fraction measurements in internal combustion engines.

    Science.gov (United States)

    Miles, P C

    1999-03-20

    An optical diagnostic system based on line imaging of Raman-scattered light has been developed to study the mixing processes in internal combustion engines. The system permits multipoint, single laser-shot measurements of CO(2), O(2), N(2), C(3)H(8), and H(2)O mole fractions with submillimeter spatial resolution. Selection of appropriate system hardware is discussed, as are subsequent data reduction and analysis procedures. Results are reported for data obtained at multiple crank angles and in two different engine flow fields. Measurements are made at 12 locations simultaneously, each location having measurement volume dimensions of 0.5 mm x 0.5 mm x 0.9 mm. The data are analyzed to obtain statistics of species mole fractions: mean, rms, histograms, and both spatial and cross-species covariance functions. The covariance functions are used to quantify the accuracy of the measured rms mole fraction fluctuations, to determine the integral length scales of the mixture inhomogeneities, and to quantify the cycle-to-cycle fluctuations in bulk mixture composition under well-mixed conditions.

  4. Cavity Enhanced Spectrometer performance assessment for greenhouse gas dry mole fraction measurement in humid air.

    Science.gov (United States)

    Laurent, Olivier; Yver Kwok, Camille; Guemri, Ali; Philippon, Carole; Rivier, Leonard; Ramonet, Michel

    2017-04-01

    Due to the high variability of the water vapor content in the atmosphere, the mole fraction of trace gas such as greenhouse gas (GHG) in the atmosphere is usually presented as mole fraction in dry air. In consequence, the first technology used for GHG measurement, gas chromatography or non-dispersive infra-red spectroscopy, required to dry the air sample prior to analysis at a dew point lower than -50°C. The emergence of new GHG analyzers using infrared Enhanced Cavity Spectroscopy which measure the water vapor content in the air sample, allows providing the dry mole fraction of GHG without any drying system upstream by applying appropriate correction of the water vapor effects (dilution, pressure broadening…). In the framework of ICOS, a European research infrastructure aiming to provide harmonized high precision data for advanced research on carbon cycle and GHG budgets over Europe, the Metrology Lab of the Atmosphere Thematic Centre (ATC), located at LSCE in France, is mainly dedicated to elaborating measurement protocols and evaluating performance of GHG analyzers. Among the different tests conducted to characterize the metrological performance, the Metrology Lab focuses on the water vapor correction to apply on the GHG measurement. Most of the analyzers tested at the Metrology Lab are based on Cavity Enhanced Spectroscopy measuring the ICOS mandatory species, CO2, CH4 and CO. This presentation presents the results of the performance assessment of the manufacturer built-in water vapor correction and the possible improvement. Thanks to the large number of instrument tested, the presentation provides a performance overview of the GHG analyzers deployed in the ICOS atmospheric station network. Finally the performance of the water vapor correction will be discussed in regard of the performance obtained by using a drying system.

  5. High accuracy measurements of dry mole fractions of carbon dioxide and methane in humid air

    Directory of Open Access Journals (Sweden)

    C. W. Rella

    2013-03-01

    Full Text Available Traditional techniques for measuring the mole fractions of greenhouse gases in the well-mixed atmosphere have required dry sample gas streams (dew point inter-laboratory compatibility goals (WMO, 2011a without drying the sample gas. In this paper, we present laboratory methodology for empirically deriving the water vapour correction factors, and we summarise a series of in-situ validation experiments comparing the measurements in humid gas streams to well-characterised dry-gas measurements. By using the manufacturer-supplied correction factors, the dry-mole fraction measurements have been demonstrated to be well within the GAW compatibility goals up to a water vapour concentration of at least 1%. By determining the correction factors for individual instruments once at the start of life, this water vapour concentration range can be extended to at least 2% over the life of the instrument, and if the correction factors are determined periodically over time, the evidence suggests that this range can be extended up to and even above 4% water vapour concentrations.

  6. Estimating regional methane surface fluxes: the relative importance of surface and GOSAT mole fraction measurements

    Directory of Open Access Journals (Sweden)

    A. Fraser

    2013-06-01

    Full Text Available We use an ensemble Kalman filter (EnKF, together with the GEOS-Chem chemistry transport model, to estimate regional monthly methane (CH4 fluxes for the period June 2009–December 2010 using proxy dry-air column-averaged mole fractions of methane (XCH4 from GOSAT (Greenhouse gases Observing SATellite and/or NOAA ESRL (Earth System Research Laboratory and CSIRO GASLAB (Global Atmospheric Sampling Laboratory CH4 surface mole fraction measurements. Global posterior estimates using GOSAT and/or surface measurements are between 510–516 Tg yr−1, which is less than, though within the uncertainty of, the prior global flux of 529 ± 25 Tg yr−1. We find larger differences between regional prior and posterior fluxes, with the largest changes in monthly emissions (75 Tg yr−1 occurring in Temperate Eurasia. In non-boreal regions the error reductions for inversions using the GOSAT data are at least three times larger (up to 45% than if only surface data are assimilated, a reflection of the greater spatial coverage of GOSAT, with the two exceptions of latitudes >60° associated with a data filter and over Europe where the surface network adequately describes fluxes on our model spatial and temporal grid. We use CarbonTracker and GEOS-Chem XCO2 model output to investigate model error on quantifying proxy GOSAT XCH4 (involving model XCO2 and inferring methane flux estimates from surface mole fraction data and show similar resulting fluxes, with differences reflecting initial differences in the proxy value. Using a series of observing system simulation experiments (OSSEs we characterize the posterior flux error introduced by non-uniform atmospheric sampling by GOSAT. We show that clear-sky measurements can theoretically reproduce fluxes within 10% of true values, with the exception of tropical regions where, due to a large seasonal cycle in the number of measurements because of clouds and aerosols, fluxes are within 15% of true fluxes. We evaluate our

  7. Current transport mechanism in graphene/AlGaN/GaN heterostructures with various Al mole fractions

    Directory of Open Access Journals (Sweden)

    Bhishma Pandit

    2016-06-01

    Full Text Available The current transport mechanism of graphene formed on AlxGa1−xN/GaN heterostructures with various Al mole fractions (x = 0.15, 0.20, 0.30, and 0.40 is investigated. The current–voltage measurement from graphene to AlGaN/GaN shows an excellent rectifying property. The extracted Schottky barrier height of the graphene/AlGaN/GaN contacts increases with the Al mole fraction in AlGaN. However, the current transport mechanism deviates from the Schottky-Mott theory owing to the deterioration of AlGaN crystal quality at high Al mole fractions confirmed by reverse leakage current measurement.

  8. Characterization of Local Carrier Dynamics in AlN and AlGaN Films using High Spatial- and Time-resolution Cathodoluminescence Spectroscopy

    Science.gov (United States)

    2012-10-12

    lifetimes with structural irregularities in the near future. Introduction: Aluminium nitride (AlN) and high AlN mole fraction AlxGa1-xN alloys have...cathodoluminescence studies on freestanding GaN substrates grown by hydride vapor phase epitaxy", Pacific Rim Meeting on Electrochemical and Solid-State Science...dynamics in freestanding GaN substrates grown by hydride vapor phase epitaxy studied using the spatio-time-resolved cathodoluminescence technique

  9. Assessing filtering of mountaintop CO2 mole fractions for application to inverse models of biosphere-atmosphere carbon exchange

    Directory of Open Access Journals (Sweden)

    S. L. Heck

    2012-02-01

    Full Text Available There is a widely recognized need to improve our understanding of biosphere-atmosphere carbon exchanges in areas of complex terrain including the United States Mountain West. CO2 fluxes over mountainous terrain are often difficult to measure due to unusual and complicated influences associated with atmospheric transport. Consequently, deriving regional fluxes in mountain regions with carbon cycle inversion of atmospheric CO2 mole fraction is sensitive to filtering of observations to those that can be represented at the transport model resolution. Using five years of CO2 mole fraction observations from the Regional Atmospheric Continuous CO2 Network in the Rocky Mountains (Rocky RACCOON, five statistical filters are used to investigate a range of approaches for identifying regionally representative CO2 mole fractions. Test results from three filters indicate that subsets based on short-term variance and local CO2 gradients across tower inlet heights retain nine-tenths of the total observations and are able to define representative diel variability and seasonal cycles even for difficult-to-model sites where the influence of local fluxes is much larger than regional mole fraction variations. Test results from two other filters that consider measurements from previous and following days using spline fitting or sliding windows are overly selective. Case study examples showed that these windowing-filters rejected measurements representing synoptic changes in CO2, which suggests that they are not well suited to filtering continental CO2 measurements. We present a novel CO2 lapse rate filter that uses CO2 differences between levels in the model atmosphere to select subsets of site measurements that are representative on model scales. Our new filtering techniques provide guidance for novel approaches to assimilating mountain-top CO2 mole fractions in carbon cycle inverse models.

  10. Water-Methanol Mixtures: Simulations of Mixing Properties over the Entire Range of Mole Fractions.

    Science.gov (United States)

    Soetens, Jean-Christophe; Bopp, Philippe A

    2015-07-09

    Numerous experimental and theoretical investigations have been devoted to the hydrogen bond in pure liquids and mixtures. Among the different theoretical approaches, molecular dynamics (MD) simulations are predominant in obtaining detailed information, on the molecular level, simultaneously on the structure and the dynamics. Water and methanol are the two most prominent hydrogen-bonded liquids, and they and their mixtures have consequently been the subject of many studies; we revisit here the problem of the mixtures. An important first step is to check whether a classical potential model, the components of which are deemed to be satisfactory for the pure liquids, is able to reproduce the known thermodynamic excess properties of the mixtures sufficiently well. We have used the available BJH (water) and PHH (methanol) flexible models because they are by construction mutually compatible and also well suited to study, in a second step, some dynamic property characteristic of hydrogen-bonded liquids. In this article we show that these models, after a slight reparametrization for use in NpT simulations, reproduce the essential features of the excess mixing and molar properties of water-methanol mixtures. Furthermore, in the pure liquids, the agreement of the radial distribution functions with experiment remains as satisfactory as before. Similarly, the translation self-diffusion coefficients D are modified by less than 10%. In the mixtures, they evolve nonmonotonously as a function of mole fraction.

  11. Determination of mole fractions of ethyl-cellulose-containing monomers by NMR.

    Science.gov (United States)

    Kono, Hiroyuki

    2017-06-05

    Three samples of ethyl cellulose (EC) with different degrees of substitution (DS)-0.51, 1.41, and 2.28-were prepared by a slurry method using ethyl bromide as the etherification reagent. 1 H- 13 C HSQC and HSQC-TOCSY NMR spectral analysis allowed for complete assignment of the 1 H and 13 C chemical shifts, respectively, of eight anhydroglucose units (AGUs) comprising EC chains-un-, 2-mono-, 3-mono-, 6-mono-, 2,3-di-, 2,6-di-, 3,6-di-, and 2,3,6-tri-substituted AGUs. In addition, the lineshape of the quantitative 13 C NMR spectra of the three EC samples provided change in the mole fractions of these AGUs against DS, making it possible to estimate the reaction mechanism for the production of EC, elucidating reactivities of the hydroxyl groups at the 2, 3, and 6 positions of cellulose and interactions between the substituent groups within the same AGU and vicinal AGUs. Copyright © 2017 Elsevier Ltd. All rights reserved.

  12. Long-term analysis of carbon dioxide and methane column-averaged mole fractions retrieved from SCIAMACHY

    Directory of Open Access Journals (Sweden)

    O. Schneising

    2011-03-01

    Full Text Available Carbon dioxide (CO2 and methane (CH4 are the two most important anthropogenic greenhouse gases contributing to global climate change. SCIAMACHY onboard ENVISAT (launch 2002 was the first and is now with TANSO onboard GOSAT (launch 2009 one of only two satellite instruments currently in space whose measurements are sensitive to CO2 and CH4 concentration changes in the lowest atmospheric layers where the variability due to sources and sinks is largest.

    We present long-term SCIAMACHY retrievals (2003–2009 of column-averaged dry air mole fractions of both gases (denoted XCO2 and XCH4 derived from absorption bands in the near-infrared/shortwave-infrared (NIR/SWIR spectral region focusing on large-scale features. The results are obtained using an upgraded version (v2 of the retrieval algorithm WFM-DOAS including several improvements, while simultaneously maintaining its high processing speed. The retrieved mole fractions are compared to global model simulations (CarbonTracker XCO2 and TM5 XCH4 being optimised by assimilating highly accurate surface measurements from the NOAA/ESRL network and taking the SCIAMACHY averaging kernels into account. The comparisons address seasonal variations and long-term characteristics.

    The steady increase of atmospheric carbon dioxide primarily caused by the burning of fossil fuels can be clearly observed with SCIAMACHY globally. The retrieved global annual mean XCO2 increase agrees with CarbonTracker within the error bars (1.80±0.13 ppm yr−1 compared to 1.81±0.09 ppm yr−1. The amplitude of the XCO2 seasonal cycle as retrieved by SCIAMACHY, which is 4.3±0.2 ppm for the Northern Hemisphere and 1.4±0.2 ppm for the Southern Hemisphere, is on average about 1 ppm larger than for CarbonTracker.

    An investigation of the boreal forest carbon uptake during the

  13. Tunable diode laser absorption spectroscopy-based tomography system for on-line monitoring of two-dimensional distributions of temperature and H2O mole fraction

    Science.gov (United States)

    Xu, Lijun; Liu, Chang; Jing, Wenyang; Cao, Zhang; Xue, Xin; Lin, Yuzhen

    2016-01-01

    To monitor two-dimensional (2D) distributions of temperature and H2O mole fraction, an on-line tomography system based on tunable diode laser absorption spectroscopy (TDLAS) was developed. To the best of the authors' knowledge, this is the first report on a multi-view TDLAS-based system for simultaneous tomographic visualization of temperature and H2O mole fraction in real time. The system consists of two distributed feedback (DFB) laser diodes, a tomographic sensor, electronic circuits, and a computer. The central frequencies of the two DFB laser diodes are at 7444.36 cm-1 (1343.3 nm) and 7185.6 cm-1 (1391.67 nm), respectively. The tomographic sensor is used to generate fan-beam illumination from five views and to produce 60 ray measurements. The electronic circuits not only provide stable temperature and precise current controlling signals for the laser diodes but also can accurately sample the transmitted laser intensities and extract integrated absorbances in real time. Finally, the integrated absorbances are transferred to the computer, in which the 2D distributions of temperature and H2O mole fraction are reconstructed by using a modified Landweber algorithm. In the experiments, the TDLAS-based tomography system was validated by using asymmetric premixed flames with fixed and time-varying equivalent ratios, respectively. The results demonstrate that the system is able to reconstruct the profiles of the 2D distributions of temperature and H2O mole fraction of the flame and effectively capture the dynamics of the combustion process, which exhibits good potential for flame monitoring and on-line combustion diagnosis.

  14. Atypical Moles

    Science.gov (United States)

    ... of developing melanoma in people with atypical moles. Melanoma is a potentially deadly form of skin cancer that is diagnosed in about 40,000 Americans each year. It is now known that about half of the people with melanoma have numerous atypical moles on their bodies. The ...

  15. The mole

    CERN Multimedia

    CERN PhotoLab

    1974-01-01

    The mole continued its way around the SPS ring ... and on 31 July emerged where it started from, having completed its 7 kilometre journey without ever veering more than a couple of centimetres from its schedule path.

  16. Applied Learning Networks (ALN)

    National Research Council Canada - National Science Library

    Bannister, Joseph; Shen, Wei-Min; Touch, Joseph; Hou, Feili; Pingali, Venkata

    2007-01-01

    Applied Learning Networks (ALN) demonstrates that a network protocol can learn to improve its performance over time, showing how to incorporate learning methods into a general class of network protocols...

  17. Tunable diode laser absorption spectroscopy-based tomography system for on-line monitoring of two-dimensional distributions of temperature and H{sub 2}O mole fraction

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Lijun, E-mail: lijunxu@buaa.edu.cn; Liu, Chang; Jing, Wenyang; Cao, Zhang [School of Instrument Science and Opto-Electronic Engineering, Beihang University, Beijing 100191 (China); Ministry of Education’s Key Laboratory of Precision Opto-Mechatronics Technology, Beijing 100191 (China); Xue, Xin; Lin, Yuzhen [School of Energy and Power Engineering, Beihang University, Beijing 100191 (China)

    2016-01-15

    To monitor two-dimensional (2D) distributions of temperature and H{sub 2}O mole fraction, an on-line tomography system based on tunable diode laser absorption spectroscopy (TDLAS) was developed. To the best of the authors’ knowledge, this is the first report on a multi-view TDLAS-based system for simultaneous tomographic visualization of temperature and H{sub 2}O mole fraction in real time. The system consists of two distributed feedback (DFB) laser diodes, a tomographic sensor, electronic circuits, and a computer. The central frequencies of the two DFB laser diodes are at 7444.36 cm{sup −1} (1343.3 nm) and 7185.6 cm{sup −1} (1391.67 nm), respectively. The tomographic sensor is used to generate fan-beam illumination from five views and to produce 60 ray measurements. The electronic circuits not only provide stable temperature and precise current controlling signals for the laser diodes but also can accurately sample the transmitted laser intensities and extract integrated absorbances in real time. Finally, the integrated absorbances are transferred to the computer, in which the 2D distributions of temperature and H{sub 2}O mole fraction are reconstructed by using a modified Landweber algorithm. In the experiments, the TDLAS-based tomography system was validated by using asymmetric premixed flames with fixed and time-varying equivalent ratios, respectively. The results demonstrate that the system is able to reconstruct the profiles of the 2D distributions of temperature and H{sub 2}O mole fraction of the flame and effectively capture the dynamics of the combustion process, which exhibits good potential for flame monitoring and on-line combustion diagnosis.

  18. Estimating surface CO2 fluxes from space-borne CO2 dry air mole fraction observations using an ensemble Kalman Filter

    Directory of Open Access Journals (Sweden)

    S. Dance

    2009-04-01

    Full Text Available We have developed an ensemble Kalman Filter (EnKF to estimate 8-day regional surface fluxes of CO2 from space-borne CO2 dry-air mole fraction observations (XCO2 and evaluate the approach using a series of synthetic experiments, in preparation for data from the NASA Orbiting Carbon Observatory (OCO. The 32-day duty cycle of OCO alternates every 16 days between nadir and glint measurements of backscattered solar radiation at short-wave infrared wavelengths. The EnKF uses an ensemble of states to represent the error covariances to estimate 8-day CO2 surface fluxes over 144 geographical regions. We use a 12×8-day lag window, recognising that XCO2 measurements include surface flux information from prior time windows. The observation operator that relates surface CO2 fluxes to atmospheric distributions of XCO2 includes: a the GEOS-Chem transport model that relates surface fluxes to global 3-D distributions of CO2 concentrations, which are sampled at the time and location of OCO measurements that are cloud-free and have aerosol optical depths 2 profiles to XCO2, accounting for differences between nadir and glint measurements, and the associated scene-dependent observation errors. We show that OCO XCO2 measurements significantly reduce the uncertainties of surface CO2 flux estimates. Glint measurements are generally better at constraining ocean CO2 flux estimates. Nadir XCO2 measurements over the terrestrial tropics are sparse throughout the year because of either clouds or smoke. Glint measurements provide the most effective constraint for estimating tropical terrestrial CO2 fluxes by accurately sampling fresh continental outflow over neighbouring oceans. We also present results from sensitivity experiments that investigate how flux estimates change with 1 bias and unbiased errors, 2 alternative duty cycles, 3 measurement density and correlations, 4 the spatial resolution of estimated flux estimates, and 5 reducing the length of the lag window and the

  19. Non-ideality of methanol solution's of artificial serum in the mole fraction range from 5 x 10(-4) to 5 x 10(-3) at 25 degrees C

    DEFF Research Database (Denmark)

    Ralloff, K.P.G.; Westh, Peter; Purssell, R.A.

    2003-01-01

    Vapour pressure and excess partial molar enthalpy were measured at 25 degreesC for solutions of methanol in H2O and artificial serum solutions. The mole fraction range studied was from 5 x 10(-4) to 5 x 10(-3). From the vapour pressure data, the partial pressures were determined by the Barker......), on the other hand, produced the osmotic coefficient significantly larger than unity in serum solutions studied. This is consistent with the findings by the earlier freezing point depression study on ethanol in human blood serum solutions. The partial molar enthalpy data indicated highly non-ideal behaviours...

  20. Absolute noninvasive measurement of CO2 mole fraction emitted by E. coli and S. aureus using calibration-free 2f WMS applied to a 2004  nm VCSEL.

    Science.gov (United States)

    Zarin, A S; Chakraborty, Arup Lal; Upadhyay, Abhishek

    2017-06-01

    We report the first demonstration, to the best of our knowledge, of accurate real-time noninvasive measurement of the absolute cumulative mole fraction of metabolic carbon dioxide emitted by Escherichia coli and Staphylococcus aureus over a period of several hours of their life cycles using a recently developed calibration-free wavelength modulation spectroscopy technique. A 1 mW vertical-cavity surface-emitting laser is used to interrogate a single rotational vibrational absorption line of carbon dioxide at 2003.5 nm. The measurements are immune to laser intensity fluctuations and variable optical coupling that is inevitable in such free-space coupled experiments that run over 10-18 h. The cumulative carbon dioxide mole fraction follows the characteristic modified Gompertz model that is typical of bacterial growth in batch cultures. The characteristic growth parameters are extracted from this curve. The technique can be readily extended to study multiple volatile organic compounds that bacteria are known to emit.

  1. Investigation on the Electrical Conductivity of Transformer Oil-Based AlN Nanofluid

    Directory of Open Access Journals (Sweden)

    M. Dong

    2013-01-01

    Full Text Available Aluminum-nitride-(AlN-transformer oil-based nanofluid was prepared by dispersing AlN nanoparticles in transformer oil. The composition-dependent electrical conductivity of AlN-transformer oil nanofluid was investigated at different ambient temperatures. The results indicate the nonlinear dependences of the electrical conductivity on volumetric fraction and temperature. In comparison to the pure transformer oil, the electrical conductivity of nanofluid containing 0.5% AlN nanoparticles has increased by 1057 times at 60°C. By considering the electrophoresis of the AlN nanoparticles, a straightforward electrical conductivity model is established to modulate and understand the experiment results.

  2. Mole gun injury.

    Science.gov (United States)

    Pistré, V; Rezzouk, J

    2013-09-01

    A mole gun is a weapon, which is used to trap and kill moles. This report provides an overview of the state of knowledge of mole gun injuries, comparable to blast injuries caused by fireworks, explosive or gunshot. Over a 2-year period, the authors reported their experience with ten hand injuries caused by mole gun. Radial side of the hand was often concerned, particularly the thumb. The authors explain their choices in the management of such lesions. Surgery was performed primarily and a large debridement currently seemed to offer the best outcome for the patient. Blast, crush, burns and lacerations may explain the higher rate of amputation to the digits. A long period of physiotherapy, specifically of the hand, was needed before the patient could return to work. This ballistic hand trauma encountered by surgeons requires knowledge and understanding of these injuries. It should be in accordance with firearms law because of severe injuries encountered and possible lethal wounds. Copyright © 2013 Elsevier Masson SAS. All rights reserved.

  3. MOLES Information Model

    Science.gov (United States)

    Ventouras, Spiros; Lawrence, Bryan; Woolf, Andrew; Cox, Simon

    2010-05-01

    The Metadata Objects for Linking Environmental Sciences (MOLES) model has been developed within the Natural Environment Research Council (NERC) DataGrid project [NERC DataGrid] to fill a missing part of the ‘metadata spectrum'. It is a framework within which to encode the relationships between the tools used to obtain data, the activities which organised their use, and the datasets produced. MOLES is primarily of use to consumers of data, especially in an interdisciplinary context, to allow them to establish details of provenance, and to compare and contrast such information without recourse to discipline-specific metadata or private communications with the original investigators [Lawrence et al 2009]. MOLES is also of use to the custodians of data, providing an organising paradigm for the data and metadata. The work described in this paper is a high-level view of the structure and content of a recent major revision of MOLES (v3.3) carried out as part of a NERC DataGrid extension project. The concepts of MOLES v3.3 are rooted in the harmonised ISO model [Harmonised ISO model] - particularly in metadata standards (ISO 19115, ISO 19115-2) and the ‘Observations and Measurements' conceptual model (ISO 19156). MOLES exploits existing concepts and relationships, and specialises information in these standards. A typical sequence of data capturing involves one or more projects under which a number of activities are undertaken, using appropriate tools and methods to produce the datasets. Following this typical sequence, the relevant metadata can be partitioned into the following main sections - helpful in mapping onto the most suitable standards from the ISO 19100 series. • Project section • Activity section (including both observation acquisition and numerical computation) • Observation section (metadata regarding the methods used to obtained the data, the spatial and temporal sampling regime, quality etc.) • Observation collection section The key concepts in

  4. Trend of Complete Hydatidiform Mole

    Directory of Open Access Journals (Sweden)

    K Thapa

    2010-03-01

    Full Text Available INTRODUCTION: Complete Hydatidiform mole is one of the most frequent abnormal pregnancies. This review studies the trend of complete mole in Paropakar Maternity and Women's hospital and clinical ability to detect it. METHODS: This is a retrospective study of 504 cases of complete hydatidiform mole recorded at Paropakar maternity and women's hospital, Kathmandu, during 2058-2065 B.S. Medical records were reviewed and incidence, clinical presentation and method of diagnosis were studied. RESULTS: During the study period, there were 13,9117 births and 504 complete moles, 12 partial moles, 48 persistent gestational tumours, six choriocarcinoma and four invasive moles recorded in the hospital. The incidence of complete mole was one per 276 births. It was prevalent among women younger than 29 years (80% and among the primigravidae (36.7%. More than 90% women presented in the first half of their pregnancy and vaginal bleeding was the main complaint (68.3%. Suction evacuation, dilation and evacuation followed by sharp curettage and abdominal hysterectomy were performed in 80.6%, 17.6% and 1.2% of the women respectively. Persistent mole and choriocarcinoma developed in 9.5% and 0.4% respectively. CONCLUSIONS: Complete mole has the highest incidence. It affects mostly younger women and presents with vaginal bleeding most of the time, usually in the first half of their pregnancy. Keywords: complete hydatidiform mole, gestational trophoblastic disease, persistent gestational tumours.

  5. The extraordinary role of the AlN interlayer in growth of AlN sputtered on Ti electrodes

    NARCIS (Netherlands)

    Tran, Tuan; Pandraud, G.; Tichelaar, F.D.; Nguyen, Duc Minh; Schellevis, H.; Sarro, P.M.

    2013-01-01

    The structure of AlN layers grown on Ti with and without an AlN interlayer between the Si substrate and the Ti layer is investigated. The AlN grains take over the orientation of the Ti columnar grains in both cases. Surprisingly, the Ti grains do not take over completely the orientations of the AlN

  6. Common Moles, Atypical Moles (Dysplastic Nevi), and Risk of Melanoma

    Science.gov (United States)

    ... Melanoma—Patient Version Moles, Dysplastic Nevi, and Melanoma Recognition Tool Skin Cancer (Including Melanoma)—Patient Version What ... government may be owned by the writer, and graphics may be owned by their creator. In such ...

  7. Vacuum Rabi splitting of exciton-polariton emission in an AlN film.

    Science.gov (United States)

    Li, Kongyi; Wang, Weiying; Chen, Zhanghai; Gao, Na; Yang, Weihuang; Li, Wei; Chen, Hangyang; Li, Shuping; Li, Heng; Jin, Peng; Kang, Junyong

    2013-12-19

    The vacuum Rabi splitting of exciton-polariton emission is observed in cathodoluminescence (CL) and photoluminescence spectra of an AlN epitaxial film. Atomic force microscopy and CL measurements show that the film has an atomically flat surface, high purity, and high crystal quality. By changing the temperature, anticrossing behavior between the upper and lower polariton branch can be obtained in low temperature with a Rabi splitting of 44 meV, in agreement with the calculation. This large energy splitting is caused by strong oscillator strength, intrinsically pure polarization in wurtzite AlN semiconductor, and high fraction of free exciton in the sample. These properties indicate that AlN can be a potential semiconductor for the further development of polariton physics and polariton-based novel devices.

  8. Pyroelectric properties of AlN

    Science.gov (United States)

    Fuflyigin, V.; Salley, E.; Osinsky, A.; Norris, P.

    2000-11-01

    Pyroelectric properties of high-quality (0001)AlN films grown on (111) Si were studied. The pyroelectric coefficient p was measured using the dynamic method. The value was in the range of 6-8 μC/(m2 K), yielding a p/ɛ figure-of-merit of 0.8-0.95. The pyroelectric coefficient was independent of temperature and applied bias. Leakage current as low as 1-2×10-9 A/cm2 was measured at 5 V on large area devices. The obtained results indicate that AlN films can be used in pyroelectric thin-film devices.

  9. Tool to Distinguish Moles from Melanoma

    Science.gov (United States)

    Moles to Melanoma: Recognizing the ABCDE Features” presents photos that show changes in individual pigmented lesions over time, and describes the different appearances of moles, dysplastic nevi, and melanomas.

  10. Moles

    Science.gov (United States)

    ... What is the FOD? Foundation Levels of Giving Governance By-Laws Committees Committee Service Conflict of Interest ... AOCD Session 2017 Fall Meeting Meeting Feedback Sponsors Corporate Members Exhibitors Information for Corporate Members Publications DermLine ...

  11. Optical properties of homoepitaxial AlN

    Energy Technology Data Exchange (ETDEWEB)

    Feneberg, Martin; Neuschl, Benjamin; Thonke, Klaus [Institut fuer Halbleiterphysik, Universitaet Ulm (Germany); Collazo, Ramon; Rice, Anthony; Sitar, Zlatko [Dept. of Mat. Sci. Engr., North Carolina State University (United States); Xie, Jinqiao; Mita, Seiji [HexaTech, Inc., Morrisville, NC (United States); Rossbach, Georg; Goldhahn, Ruediger [Institut fuer Physik, TU Ilmenau (Germany); Roeppischer, Marcus; Cobet, Christoph; Esser, Norbert [ISAS, Berlin (Germany)

    2010-07-01

    Homoepitaxial c- and m-plane AlN layers, deposited by MOCVD on bulk PVT AlN are investigated by means of high resolution photoluminescence and spetroscopic ellipsometry. We find donor bound exciton lines with a full width at half maximum below 500 {mu}eV at T=10 K. The exciton binding energy amounts to 52 meV in the c-plane sample leading to a bandgap energy of 6.092 eV (at 10 K). By spectroscopic ellipsometry we access both the ordinary and the extraordinary dielectric functions. The analysis of the sharp free exciton resonance found in the extraordinary tensor components yields a transition energy being in excellent agreement with the emission studies. The ordinary component exhibits a feature which indicates a strong contribution of exciton-phonon interaction to the absorption process.

  12. AlN piezoelectric films for sensing and actuation

    NARCIS (Netherlands)

    Tran, A.T.

    2014-01-01

    Aluminum Nitride (AlN) is explored as a thin film material for piezoelectric MEMS applications. A pulse DC reactive sputtering technique is used to deposit the AlN thin films and process parameters are optimized to obtain good crystallinity and high c-axis orientation films. A CMOS compatible

  13. Ferromagnetism in Cr-doped passivated AlN nanowires

    KAUST Repository

    Kanoun, Mohammed

    2014-01-01

    We apply first principles calculations to predict the effect of Cr doping on the electronic and magnetic properties of passivated AlN nanowires. We compare the energetics of the possible dopant sites and demonstrate the favorable configuration ferromagnetic ordering. The charge density of the pristine passivated AlN nanowires is used to elucidate the bonding character. Spin density maps demonstrate an induced spin polarization for N atoms next to dopant atoms, though most of the magnetism is carried by the Cr atoms. Cr-doped AlN nanowires turn out to be interesting for spintronic devices. © 2014 the Partner Organisations.

  14. Thermoluminescence properties of AlN ceramics

    DEFF Research Database (Denmark)

    Trinkler, L.; Christensen, P.; Agersnap Larsen, N.

    1998-01-01

    The paper describes thermoluminescence (TL) properties of AlN:Y2O3 ceramics irradiated with ionising radiation. A high TL sensitivity of AlN:Y2O3 ceramics to radiation encouraged a study of the AlN ceramics for application as a dosimetric material. The paper presents experimental data on: glow...... curve, emission spectrum, dose response, energy dependence, influence of heating rate and fading rate. The measured TL characteristics were compared with those of well-known, widely used TLDs, i.e. LiF:Mg,Ti, LiF:Mg,Cu,P and Al2O3:C. It is concluded that AlN:Y2O3 ceramics showing a radiation sensitivity...

  15. Broadband dielectric response of AlN ceramic composites

    Directory of Open Access Journals (Sweden)

    Iryna V. Brodnikovska

    2014-03-01

    Full Text Available Aluminium nitride (AlN is considered as a substrate material for microelectronic applications. AlN ceramic composites with different amount of TiO2 (up to 4 vol.% were obtained using hot pressing at different sintering temperature from 1700 to 1900 °C. It was shown that milling of the raw AlN powder has strongly influence on sintering and improves densification. Broadband dielectric spectroscopy was used as a nondestructive method for monitoring of the ceramic microstructures. TiO2 additive affects the key properties of AlN ceramics. Thus, porosity of 0.1 %, dielectric permeability of σ = 9.7 and dielectric loss tangent of tanδ = 1.3·10-3 can be achieved if up to 2 vol.% TiO2 is added.

  16. Potential of AlN nanostructures as hydrogen storage materials.

    Science.gov (United States)

    Wang, Qian; Sun, Qiang; Jena, Puru; Kawazoe, Yoshiyuki

    2009-03-24

    The capability of AlN nanostructures (nanocages, nanocones, nanotubes, and nanowires) to store hydrogen has been studied using gradient-corrected density functional theory. In contrast to bulk AlN, which has the wurtzite structure and four-fold coordination, the Al sites in AlN nanostructures are unsaturated and have two- and three-fold coordination. Each Al atom is capable of binding one H(2) molecule in quasi-molecular form, leading to 4.7 wt % hydrogen, irrespective of the topology of the nanostructures. With the exception of AlN nanotubes, energetics does not support the adsorption of additional hydrogen. The binding energies of hydrogen to these unsaturated metal sites lie in the range of 0.1-0.2 eV/H(2) and are ideal for applications under ambient thermodynamic conditions. Furthermore, these materials do not suffer from the clustering problem that often plagues metal-coated carbon nanostructures.

  17. Significantly enhanced mechanical properties in AlN helix

    Science.gov (United States)

    Zhang, Xinghong; Zhao, Chaoliang; Yao, Tai; Zhou, Shanbao; Han, Jiecai; Li, Jiajie; Gao, Tangling; Wang, Xianjie; Zheng, Kun; Song, Bo

    2017-07-01

    To safely and reliably use aluminum nitride (AlN) helices in the fabrication of novel micro/nanodevices, it is very important to know their mechanical properties. Herein, we investigate the mechanical properties of individual AlN helices using an in situ tensile-bending test. Tensile tests reveal that an AlN helix has an average ε of ∼4.7 ± 0.8% elastic deformation before a typical brittle fracture occurs. The bending test shows a two-step mechanical feature—linear-elastic followed by an elastic-plastic process—with an average ε bent of ∼54.5 ± 0.6%. Our results provide direct cognition about the mechanical properties of AlN helices and their benefit to the design of AlN-based flexible micro/nanodevices.

  18. Moles and Mole Control on British Farms, Amenities and Gardens after Strychnine Withdrawal

    Directory of Open Access Journals (Sweden)

    Sandra E. Baker

    2016-06-01

    Full Text Available Moles are considered pests in Britain, but this issue has been little studied. Lower welfare standards have been tolerated for moles than for most other managed wild mammal species, as use of both the controversial poison, strychnine, and unregulated traps have been permitted. Strychnine was withdrawn in 2006 and there were fears that mole populations would increase as a result. In 2007, we conducted a comprehensive, nationwide survey of land manager perceptions, opinions and behaviour regarding moles and mole control on farms, amenities and domestic gardens in Britain. We surveyed 2150 land managers (achieving a 59% response rate and ground-truthed 29 responses. Moles were reported to be present on most farms and amenities, and 13% of gardens, and were more common in lighter soils. Where present, moles were usually considered pests, this being more likely in Wales, Scotland and northern England, on livestock and mixed farms, and on large, high-value amenities, e.g., racecourses and golf courses. Mole control followed similar patterns to mole presence. More control may occur than is economically, and therefore potentially ethically, justified. Control should be more carefully considered and, where necessary, more effectively targeted. Kill-trapping was the favoured recent and future method on farms and amenities, even if strychnine was to be reintroduced; however, because mole traps are currently unregulated, some might not meet current welfare standards if tested. We found no evidence for an increase in moles since a farm questionnaire survey conducted in 1992; this could have wider implications for future wildlife management policy changes.

  19. The mechanical and tribological properties of UHMWPE loaded ALN after mechanical activation for joint replacements.

    Science.gov (United States)

    Gong, Kemeng; Qu, Shuxin; Liu, Yumei; Wang, Jing; Zhang, Yongchao; Jiang, Chongxi; Shen, Ru

    2016-08-01

    Ultra-high molecular weight polyethylene (UHMWPE) loaded with alendronate sodium (ALN) has tremendous potential as an orthopeadic biomaterial for joint replacements. However, poor mechanical and tribological properties of UHMWPE-ALN are still obstacle for further application. The purpose of this study was to investigate the effect and mechanism of mechanical activation on mechanical and tribological properties of 1wt% ALN-loaded UHMWPE (UHMWPE-ALN-ma). In this study, tensile test, small punch test and reciprocating sliding wear test were applied to characterize the mechanical and tribological properties of UHMWPE-ALN-ma. Scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and Fourier transform infrared spectroscopy (FTIR) were employed to characterize UHMWPE-ALN-ma. Tensile test and small punch test showed that Young׳s modulus, tensile strength and work-to-failure (WTF) of UHMWPE-ALN-ma increased significantly compared to those of UHMWPE-ALN. The friction coefficients and wear factors of UHMWPE-ALN-ma both decreased significantly compared to those of UHMWPE-ALN. Mechanical activation obviously reduced type 1 (void) and type 2 (the disconnected and dislocated machining marks) fusion defects of UHMWPE-ALN-ma, which were revealed by SEM images of freeze fracture surfaces after etching and lateral surfaces of specimens after extension to fracture, respectively. It was attributed to peeled-off layers and chain scission of molecular chains of UHMWPE particles after mechanical activation, which were revealed by SEM images and FTIR spectra of UHMWPE-ALN-ma and UHMWPE-ALN, respectively. Moreover, EDS spectra revealed the more homogeneous distribution of ALN in UHMWPE-ALN-ma compared to that of UHMWPE-ALN. The present results showed that mechanical activation was a potential strategy to improve mechanical and tribological properties of UHMWPE-ALN-ma as an orthopeadic biomaterial for joint replacements. Copyright © 2016 Elsevier Ltd. All rights reserved.

  20. Puente Alnö – Suecia

    Directory of Open Access Journals (Sweden)

    Editorial, Equipo

    1974-07-01

    Full Text Available This bridge that joins the island of Alnô with the peninsula near the port of Sundsvall In the north of Sweden is one of the many of prestressed concrete that have been constructed lately all over the world with the system of successive corbels. Until recently it was the longest bridge in the country and distinguishes itself by the elegance and slenderness of its longer arches and by the deep foundation system used to construct the four central bridge piers. It has been planned and constructed by Skanska Cementgjuteriet, a firm that is specializing in this type of structure.Este puente, que une la isla de Alno con la península, cerca del puerto de Sundsvall, en el norte de Suecia, es uno de los muchos de hormigón pretensado que se han construido últimamente en todo el mundo por el sistema de voladizos sucesivos. Hasta hace poco era el puente más largo del país y destaca por la elegancia y esbeltez de sus arcos más largos y por el sistema de cimentación profunda empleado para construir las cuatro pilas centrales. Ha sido proyectado y construido por Skanska Cementgjuteriet, empresa que se ha especializado en este tipo de estructura.

  1. Electronic structures of the F-terminated AlN nanoribbons

    Indian Academy of Sciences (India)

    2012-03-05

    terminated AlN nanoribbons with both zigzag and armchair edges are studied. The results show that both the zigzag and armchair AlN nanoribbons are semiconducting and nonmagnetic, and the indirect band gap of the zigzag ...

  2. Reproductive features of the eastern mole (Scalopus aquaticus) and star-nose mole (Condylura cristata).

    Science.gov (United States)

    Bedford, J M; Mock, O B; Nagdas, S K; Winfrey, V P; Olson, G E

    1999-11-01

    Since moles are closely related to shrews, the gametes and reproductive tracts of the star-nose mole (Condylura cristata) and the eastern mole (Scalopus aquaticus) were examined to gain further insight into unusual reproductive traits of the Soricidae. Moles display many of these soricid traits, but with some important differences. The cumulus oophorus of Scalopus, ovulated about 16 h after hCG injection, was largely dispersed by hyaluronidase and, though quite dense, was nevertheless more similar to that of higher mammals than to the compact 'ball of the soricid cumulus. Within the female tract in these moles, approximately 85% of the length of the oviduct comprises a narrow ampulla with numerous differentiated crypts that, in shrews, house spermatozoa. However, in contrast to shrews, moles produce considerably larger numbers of spermatozoa, which challenges the proposal that, in shrews, oviductal sperm crypts specifically permit lower sperm production by the males. In the sperm head of these two moles, the acrosome displays the long rostrum that is typical of other Insectivora, and the perforatorium has the barbs by which soricid spermatozoa probably bind to the zona pellucida. Perhaps allied to this, immunoblots indicated that the immunoreactive acrosomal matrix of Scalopus spermatozoa is simpler than the polypeptide complex of the bovine and hamster acrosomal matrix.

  3. Electronic structures of the F-terminated AlN nanoribbons

    Indian Academy of Sciences (India)

    Using the first-principles calculations, electronic properties for the F-terminated AlN nanoribbons with both zigzag and armchair edges are studied. The results show that both the zigzag and armchair AlN nanoribbons are semiconducting and nonmagnetic, and the indirect band gap of the zigzag AlN nanoribbons and the ...

  4. Surface Micromachining Process for the Integration of AlN Piezoelectric Microstructures

    NARCIS (Netherlands)

    Saravanan, S.; Berenschot, Johan W.; Krijnen, Gijsbertus J.M.; Elwenspoek, Michael Curt

    2004-01-01

    We report a novel micromachining process to fabricate AlN (Aluminum Nitride) piezoelectric microstructures for actuator applications. Piezoelectric AlN thin films can be grown with (002) preferential orientation by means of RF reactive sputtering on various substrates. For this study, AlN was

  5. Spectrophotometry mole ratio and continuous variation experiments ...

    African Journals Online (AJOL)

    For spectrophotometric determinations of various metal (M) to ligand (L) ratio's in dithizonato metal complexes this reagent provides a versatile alternative for undergraduate chemistry practicals that is cost-effective, yielding repeatable results. The mole-ratio method yield a ratio of 1M : 1L for the silver dithizonate complex ...

  6. Social structure predicts genital morphology in African mole-rats.

    Directory of Open Access Journals (Sweden)

    Marianne L Seney

    2009-10-01

    Full Text Available African mole-rats (Bathyergidae, Rodentia exhibit a wide range of social structures, from solitary to eusocial. We previously found a lack of sex differences in the external genitalia and morphology of the perineal muscles associated with the phallus in the eusocial naked mole-rat. This was quite surprising, as the external genitalia and perineal muscles are sexually dimorphic in all other mammals examined. We hypothesized that the lack of sex differences in naked mole-rats might be related to their unusual social structure.We compared the genitalia and perineal muscles in three African mole-rat species: the naked mole-rat, the solitary silvery mole-rat, and the Damaraland mole-rat, a species considered to be eusocial, but with less reproductive skew than naked mole-rats. Our findings support a relationship between social structure, mating system, and sexual differentiation. Naked mole-rats lack sex differences in genitalia and perineal morphology, silvery mole-rats exhibit sex differences, and Damaraland mole-rats are intermediate.The lack of sex differences in naked mole-rats is not an attribute of all African mole-rats, but appears to have evolved in relation to their unusual social structure and reproductive biology.

  7. Social structure predicts genital morphology in African mole-rats.

    Science.gov (United States)

    Seney, Marianne L; Kelly, Diane A; Goldman, Bruce D; Sumbera, Radim; Forger, Nancy G

    2009-10-15

    African mole-rats (Bathyergidae, Rodentia) exhibit a wide range of social structures, from solitary to eusocial. We previously found a lack of sex differences in the external genitalia and morphology of the perineal muscles associated with the phallus in the eusocial naked mole-rat. This was quite surprising, as the external genitalia and perineal muscles are sexually dimorphic in all other mammals examined. We hypothesized that the lack of sex differences in naked mole-rats might be related to their unusual social structure. We compared the genitalia and perineal muscles in three African mole-rat species: the naked mole-rat, the solitary silvery mole-rat, and the Damaraland mole-rat, a species considered to be eusocial, but with less reproductive skew than naked mole-rats. Our findings support a relationship between social structure, mating system, and sexual differentiation. Naked mole-rats lack sex differences in genitalia and perineal morphology, silvery mole-rats exhibit sex differences, and Damaraland mole-rats are intermediate. The lack of sex differences in naked mole-rats is not an attribute of all African mole-rats, but appears to have evolved in relation to their unusual social structure and reproductive biology.

  8. PEALD AlN: Controlling growth and film crystallinity

    NARCIS (Netherlands)

    Banerjee, Sourish; Aarnink, Antonius A.I.; van de Kruijs, Robbert Wilhelmus Elisabeth; Kovalgin, Alexeij Y.; Schmitz, Jurriaan

    2015-01-01

    We report on the growth kinetics and material properties of aluminium nitride (AlN) films deposited on Si(111), with plasma enhanced atomic layer deposition (PEALD). Tri-methyl aluminium (TMA) and NH3-plasma were used as the precursors. The ALD window was identified in terms of the process

  9. Prevalence of Toxoplasma gondii in common moles (Talpa europaea)

    NARCIS (Netherlands)

    Krijger, I.M.; Cornelissen, J.B.W.J.; Wisselink, H.J.; Meerburg, B.G.

    2014-01-01

    Background The prevalence of Toxoplasma gondii in common moles, Talpa europaea, was investigated in order to determine whether moles can serve as an indicator species for T. gondii infections in livestock. Findings In total, 86 moles were caught from 25 different sites in the Netherlands. Five

  10. Definition of the mole (IUPAC Recommendation 2017)

    OpenAIRE

    Marquardt, Roberto; Meija, Juris; Mester, Zoltán; Towns, Marcy; Weir, Ron; Davis, Richard; Stohner, Jürgen

    2018-01-01

    In 2011 the General Conference on Weights and Measures (CGPM) noted the intention of the International Committee for Weights and Measures (CIPM) to revise the entire International System of Units (SI) by linking all seven base units to seven fundamental physical constants. Of particular interest to chemists, new definitions for the kilogram and the mole have been proposed. A recent IUPAC Technical Report discussed these new definitions in relation to immediate consequences for the chemical co...

  11. Structural, magnetic and microwave properties of barium hexaferrite thick films with different Fe/Ba mole ratio

    Energy Technology Data Exchange (ETDEWEB)

    Verma, Samiksha [School of Physics and Materials Science, Thapar University, Patiala 147004 (India); Dhawan, S.K. [Polymeric & Soft Materials Section, National Physical laboratory, New Delhi 119912 (India); Paesano, Andrea [Departamento de Fisica, Universidade Estadual de Maringá, Av. Colombo 5790, Maringá (Brazil); Pandey, O.P. [School of Physics and Materials Science, Thapar University, Patiala 147004 (India); Sharma, Puneet, E-mail: puneet.sharma@thapar.edu [School of Physics and Materials Science, Thapar University, Patiala 147004 (India)

    2015-12-15

    Barium hexaferrite (BaFe{sub 12}O{sub 19}) thick films (∼60 µm) with different BaO·xFe{sub 2}O{sub 3} mole ratio (x=5.0–6.0) were prepared by screen printing method. X-ray diffraction analysis confirmed the formation of single phase BaFe{sub 12}O{sub 19} (BaM). Preferential site occupation of Fe{sup 3+} ion at five different crystallographic sites, with varied mole ratio was measured by Mössbauer spectroscopy. Vacancy fraction found to be higher at 4f{sub 1}, 4f{sub 2} and 2b sites for mole ratio 5.5 and 5.0 respectively. Magnetic measurement shows that the magnetization (M) and magnetocrystalline anisotropy field (H{sub a}) depends upon mole ratio. M and H{sub a} are found to be maximum for mole ratio 5.5, while the coercivity (H{sub c}) remains constant. Reflection losses (R{sub L}) in the frequency range of 12–18 GHz were also studied. Present investigation demonstrates the effect of mole ratio on structural, magnetic and microwave absorption properties of BaM thick films for microwave device applications. - Highlights: • Single phase BaM thick films with different Fe/Ba mole ratio are prepared. • Site preference of Fe ion is estimated by Mössbauer spectroscopy. • Magnetization and magnetocrystalline ansisotropy is found maximum for 5.5 mole ratio. • Absorption frequency found to vary with the mole ratio.

  12. ALnS2:RE (A=K, Rb; Ln=La, Gd, Lu, Y): New optical materials family

    International Nuclear Information System (INIS)

    Jarý, V.; Havlák, L.; Bárta, J.; Mihóková, E.; Buryi, M.; Nikl, M.

    2016-01-01

    In the presented review paper, new potentially interesting material family, RE-doped ternary sulfides ALnS 2 (RE=Ce, Pr, Sm, Eu, Tb, Tm; A=Rb, K; Ln=La, Gd, Lu, Y) is discussed. Their synthesis is described and the structural and optical properties, characterized by methods of X-ray diffraction, time-resolved luminescence spectroscopy and electron paramagnetic resonance, are summarized and reviewed especially with respect to the influence of their composition. All samples discussed were synthesized in the form of transparent crystalline hexagonal platelets by chemical reaction under the flow of hydrogen sulfide. Their luminescence characteristics, including absorption, radioluminescence, photoluminescence excitation and emission spectra and decay kinetics, were measured and evaluated in a broad temperature (8–800 K) and concentration (0.002–20% of dopants) range. The application potential of mentioned compounds in the field of white LED solid state lightings or X-ray phosphors is thoroughly discussed. - Highlights: • RE-doped ALnS 2 (A=K, Rb; Ln=La, Gd, Lu, Y) were synthesized. • Their optical characteristics are summarized. • Concentration and temperature dependences of luminescence features investigated. • EPR technique is employed to explain Eu 2+ incorporation into KLuS 2 host. • The application potential in white LED and X-ray phosphors is discussed.

  13. Ultrasonographic findings of hydatidiform mole and missed abortion

    International Nuclear Information System (INIS)

    Yun, Kwang Myeong; Lee, Yeong Hwan; Chung, Hye Kyeong; Chung, Duck Soo; Kim, Ok Dong

    1990-01-01

    To establish the sonographic characteristics of the hydatidiform mole and the missed abortion with placental degeneration, we have retrospectively analyzed 12 cases of complete mole, 10 cases of partial mole, and 10 cases of missed abortion with placental hydropic degeneration, collected at Taegu Catholic General Hospital, from January 1986 to December 1989. The results were as follows : 1. Of 12 cases of complete mole, all demonstrated diffuse intrauterine vesicular pattern of internal echo without a gestational sac. Two cases were recurred after D and E. 2. The partial mole was characterized by focal (70%) or diffuse (20%) distribution of hydatidiform placental change and a gestational sac (100%) with or without a macerated fetus. But the striking hydatidiform placental change was not present in one cases of partial mole. 3. The uterus was larger for dates in 9 cases (90%) of complete mole, but smaller for dates in 7 cases (70%) of partial mole. 4. The missed abortion with placental hydropic degeneration was indistinguished from a partial mole due to their similar sonographic appearance : focal or diffuse cystic change of a placenta, a distorted gestational sac with or without a fetus, and a smaller uterus for dates. On conclusion, the complete mole could be easily distinguished from a partial mole or a missed abortion by sonography : a gestational sac or an area of noncystic placenta was not identified in a complete mole. The partial mole was indistinguished from a missed abortion, but if there is the suspicion of trophoblastic proliferation, such as a convex placental surface or a larger uterus for dates, then the diagnosis is probably a partial mole rather than a missed abortion

  14. Instrumented Moles for Planetary Subsurface Regolith Studies

    Science.gov (United States)

    Richter, L. O.; Coste, P. A.; Grzesik, A.; Knollenberg, J.; Magnani, P.; Nadalini, R.; Re, E.; Romstedt, J.; Sohl, F.; Spohn, T.

    2006-12-01

    Soil-like materials, or regolith, on solar system objects provide a record of physical and/or chemical weathering processes on the object in question and as such possess significant scientific relevance for study by landed planetary missions. In the case of Mars, a complex interplay has been at work between impact gardening, aeolian as well as possibly fluvial processes. This resulted in regolith that is texturally as well as compositionally layered as hinted at by results from the Mars Exploration Rover (MER) missions which are capable of accessing shallow subsurface soils by wheel trenching. Significant subsurface soil access on Mars, i.e. to depths of a meter or more, remains to be accomplished on future missions. This has been one of the objectives of the unsuccessful Beagle 2 landed element of the ESA Mars Express mission having been equipped with the Planetary Underground Tool (PLUTO) subsurface soil sampling Mole system capable of self-penetration into regolith due to an internal electro-mechanical hammering mechanism. This lightweight device of less than 900 g mass was designed to repeatedly obtain and deliver to the lander regolith samples from depths down to 2 m which would have been analysed for organic matter and, specifically, organic carbon from potential extinct microbial activity. With funding from the ESA technology programme, an evolved Mole system - the Instrumented Mole System (IMS) - has now been developed to a readiness level of TRL 6. The IMS is to serve as a carrier for in situ instruments for measurements in planetary subsurface soils. This could complement or even eliminate the need to recover samples to the surface. The Engineering Model hardware having been developed within this effort is designed for accommodating a geophysical instrument package (Heat Flow and Physical Properties Package, HP3) that would be capable of measuring regolith physical properties and planetary heat flow. The chosen design encompasses a two-body Mole

  15. Results from a trainable UT instrument - ALN 4060

    International Nuclear Information System (INIS)

    Behravesh, M.

    1984-01-01

    The ALN 4060 Flaw Discriminator is a Z-80 microprocessor based ultrasonic flaw detector/discriminator which is operator trainable on up to three classes of reflectors. It can be applied to any testing situations where normal pulse-echo ultrasonics are used. Received ultrasonic RF waveforms are digitized (at operator selectable rates of up to 160 MHz) before processing and thereafter all internal operations and displays, as well as operator interfaces, are performed in digital mode. The system can be trained to recognize and discriminate between reflectors and can be used in analyses to recognize and classify reflectors by their waveform signatures. In this paper a summary is presented of the evaluation results and the operational experiences that were obtained by the Electrical Power Research Institute nondestructive examination centre in the application of the ALN 4060 to the problem of inspection of intergranular stress corrosion cracks in stainless steel pipes of boiling water reactors. (U.K.)

  16. Growth of AlN by vectored flow epitaxy

    Science.gov (United States)

    Clayton, A. J.; Khandekar, A. A.; Kuech, T. F.; Mason, N. J.; Robinson, M. F.; Watkins, S.; Guo, Y.

    2007-01-01

    The growth of AlN using ammonia and trimethylaluminium is reported using a novel technique, vectored flow epitaxy. The reactor is designed to pre-crack the ammonia, run at atmospheric pressure and keep the precursors spatially separated to avoid the gas-phase interaction that can lead to an involatile adduct. These three innovations have allowed the growth of high-quality AlN at over 2 μm/h with a V/III ratio of only 50:1 at very high group III efficiencies. The precursor separation also leads to a dust-free environment with no appreciable filter load even after the growth of 100 μm of material.

  17. Structural, magnetic and microwave properties of barium hexaferrite thick films with different Fe/Ba mole ratio

    Science.gov (United States)

    Verma, Samiksha; Dhawan, S. K.; Paesano, Andrea; Pandey, O. P.; Sharma, Puneet

    2015-12-01

    Barium hexaferrite (BaFe12O19) thick films (∼60 μm) with different BaO·xFe2O3 mole ratio (x=5.0-6.0) were prepared by screen printing method. X-ray diffraction analysis confirmed the formation of single phase BaFe12O19 (BaM). Preferential site occupation of Fe3+ ion at five different crystallographic sites, with varied mole ratio was measured by Mössbauer spectroscopy. Vacancy fraction found to be higher at 4f1, 4f2 and 2b sites for mole ratio 5.5 and 5.0 respectively. Magnetic measurement shows that the magnetization (M) and magnetocrystalline anisotropy field (Ha) depends upon mole ratio. M and Ha are found to be maximum for mole ratio 5.5, while the coercivity (Hc) remains constant. Reflection losses (RL) in the frequency range of 12-18 GHz were also studied. Present investigation demonstrates the effect of mole ratio on structural, magnetic and microwave absorption properties of BaM thick films for microwave device applications.

  18. Berkovich Nanoindentation on AlN Thin Films

    Directory of Open Access Journals (Sweden)

    Jian Sheng-Rui

    2010-01-01

    Full Text Available Abstract Berkovich nanoindentation-induced mechanical deformation mechanisms of AlN thin films have been investigated by using atomic force microscopy (AFM and cross-sectional transmission electron microscopy (XTEM techniques. AlN thin films are deposited on the metal-organic chemical-vapor deposition (MOCVD derived Si-doped (2 × 1017 cm−3 GaN template by using the helicon sputtering system. The XTEM samples were prepared by means of focused ion beam (FIB milling to accurately position the cross-section of the nanoindented area. The hardness and Young’s modulus of AlN thin films were measured by a Berkovich nanoindenter operated with the continuous contact stiffness measurements (CSM option. The obtained values of the hardness and Young’s modulus are 22 and 332 GPa, respectively. The XTEM images taken in the vicinity regions just underneath the indenter tip revealed that the multiple “pop-ins” observed in the load–displacement curve during loading are due primarily to the activities of dislocation nucleation and propagation. The absence of discontinuities in the unloading segments of load–displacement curve suggests that no pressure-induced phase transition was involved. Results obtained in this study may also have technological implications for estimating possible mechanical damages induced by the fabrication processes of making the AlN-based devices.

  19. High-quality AlN films grown on chemical vapor-deposited graphene films

    Directory of Open Access Journals (Sweden)

    Chen Bin-Hao

    2016-01-01

    Full Text Available We report the growth of high-quality AlN films on graphene. The graphene films were synthesized by CVD and then transferred onto silicon substrates. Epitaxial aluminum nitride films were deposited by DC magnetron sputtering on both graphene as an intermediate layer and silicon as a substrate. The structural characteristics of the AlN films and graphene were investigated. Highly c-axis-oriented AlN crystal structures are investigated based on the XRDpatterns observations.

  20. Effect of dual buffer layer structure on the epitaxial growth of AlN on sapphire

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, D.G., E-mail: dgzhao@red.semi.ac.cn [State Key Laboratory on Integrated Optoelectronics, Institute of Semiconductors, Chinese Academy of Sciences, P.O. Box 912, Beijing 100083 (China); Jiang, D.S.; Wu, L.L.; Le, L.C.; Li, L.; Chen, P.; Liu, Z.S. [State Key Laboratory on Integrated Optoelectronics, Institute of Semiconductors, Chinese Academy of Sciences, P.O. Box 912, Beijing 100083 (China); Zhu, J.J.; Wang, H.; Zhang, S.M. [Suzhou Institute of Nano-tech and Nano-bionics, Chinese Academy of Sciences, Suzhou 215125 (China); Yang, H. [State Key Laboratory on Integrated Optoelectronics, Institute of Semiconductors, Chinese Academy of Sciences, P.O. Box 912, Beijing 100083 (China); Suzhou Institute of Nano-tech and Nano-bionics, Chinese Academy of Sciences, Suzhou 215125 (China)

    2012-12-15

    Highlights: Black-Right-Pointing-Pointer A dual AlN buffer layer structure is proposed to grow AlN films. Black-Right-Pointing-Pointer AlN films could be improved obviously by using the dual AlN buffer layer. Black-Right-Pointing-Pointer The physical mechanism are discussed. - Abstract: A dual AlN buffer layer structure, including an isolated layer and a nucleation layer, is proposed to improve the growth of AlN films on sapphire substrate by metal organic chemical vapor deposition. This method is aimed to weaken the negative nitridation effect and improve lateral growth condition in the initial growth stage. It is found that suitably increasing the thickness of the nucleation layer is in favor of a better structural quality of the AlN film. An examination of surface morphology by atomic force microscopy suggests that the thicker the dual AlN buffer layer, the rougher the surface, and a higher quality of AlN epilayer is resulted.

  1. Cobalt nanoparticles deposited and embedded in AlN: Magnetic, magneto-optical, and morphological properties

    International Nuclear Information System (INIS)

    Huttel, Y.; Gomez, H.; Clavero, C.; Cebollada, A.; Armelles, G.; Navarro, E.; Ciria, M.; Benito, L.; Arnaudas, J.I.; Kellock, A.J.

    2004-01-01

    We present a structural, morphological, magnetic, and magneto-optical study of cobalt nanoparticles deposited on 50 A ring AlN/c-sapphire substrates and embedded in an AlN matrix. The dependence of the properties of Co nanoclusters deposited on AlN with growth temperature and amount of deposited Co are studied and discussed. Also we directly compare the properties of as grown and AlN embedded Co nanoclusters and show that the AlN matrix has a strong impact on their magnetic and magneto-optical properties

  2. Synthesis and characterization of straight and stacked-sheet AlN nanowires with high purity

    International Nuclear Information System (INIS)

    Lei, M.; Yang, H.; Li, P.G.; Tang, W.H.

    2008-01-01

    Large-scale AlN nanowires with hexagonal crystal structure were synthesized by the direct nitridation method at high temperatures. The experimental results indicate that these single-crystalline AlN nanowires have high purity and consist of straight and stacked-sheet nanowires. It is found that straight AlN nanowire grows along [1, 1, -2, 0] direction, whereas the stacked-sheet nanowire with hexagonal cross section is along [0 0 0 1] direction. It is thought that vapor-solid (VS) mechanism should be responsible for the growth of AlN nanowires

  3. Enhancement of c-axis texture of AlN films by substrate implantation

    International Nuclear Information System (INIS)

    Chen, C.H.; Yeh, J.M.; Hwang, J.

    2005-01-01

    Highly oriented AlN films are successfully deposited on B + implanted Si(1 1 1) substrates in a radio frequency inductively coupled plasma (RF/ICP) system. The implanted energy and dose used for the B + implanted Si(1 1 1) substrates are 200 keV and 10 15 cm -2 , respectively. The c-axis texture of AlN films can be affected by RF gun power and ion implantation. Experimental results show that the full width at half-maximum (FWHM) of AlN(0 0 2) in the X-ray rocking curve measurements decreases with increasing RF gun power. The optimum condition is at 500 W, where the FWHM of the AlN films deposited on Si(1 1 1) with and without B + implantation are 2.77 and 3.17, respectively. In average, the FWHM of the AlN films on B + implanted Si(1 1 1) are less than those on Si(1 1 1) by a factor of ∼10%. The enhancement of c-axis of AlN films due to B + implantation is attributed to the reduction of AlN grains. Raman spectra also suggest that ion implantation plays a role in reducing the tensile stress in AlN films deposited on B + implanted Si(1 1 1)

  4. Effects of AlN Coating Layer on High Temperature Characteristics of Langasite SAW Sensors

    Directory of Open Access Journals (Sweden)

    Lin Shu

    2016-09-01

    Full Text Available High temperature characteristics of langasite surface acoustic wave (SAW devices coated with an AlN thin film have been investigated in this work. The AlN films were deposited on the prepared SAW devices by mid-frequency magnetron sputtering. The SAW devices coated with AlN films were measured from room temperature to 600 °C. The results show that the SAW devices can work up to 600 °C. The AlN coating layer can protect and improve the performance of the SAW devices at high temperature. The SAW velocity increases with increasing AlN coating layer thickness. The temperature coefficients of frequency (TCF of the prepared SAW devices decrease with increasing thickness of AlN coating layers, while the electromechanical coupling coefficient (K2 of the SAW devices increases with increasing AlN film thickness. The K2 of the SAW devices increases by about 20% from room temperature to 600 °C. The results suggest that AlN coating layer can not only protect the SAW devices from environmental contamination, but also improve the K2 of the SAW devices.

  5. ACTIVITY PATTERNS IN THE MOLE-RATS TACHYORYCTES ...

    African Journals Online (AJOL)

    When fully recovered from the effects of the anaesthetic (30 to 60 minutes) the mole-rate was released into its original burrow system. Once back in the burrow, the mole- rat appeared to act normally and would rapidly seal the opening in its burrow with soil. Using a portable Geiger-Miiller counter with earphones (Beta Probe ...

  6. Aseasonal reproduction in the Hottentot golden mole, Amblysomus ...

    African Journals Online (AJOL)

    The Hottentot golden mole, Amblysomus hottentotus, is a subterranean mammal that exhibits aseasonal breeding. Reproductive organs of golden moles that had been killed on a monthly basis over a period of one year were examined. Reproductive tract measurements and body mass of each individual was measured and ...

  7. Hydatidiform mole in Aminu Kano teaching hospital, northwestern ...

    African Journals Online (AJOL)

    Background: Hydatidiform mole is a benign tumour of the trophoblast tissue and a relatively common gynaecological emergency. It could resolve spontaneously following evacuation, however 9-20% of patients with complete hydatidiform mole go on to have gestational trophoblast neoplasia. It is potentially curable once the ...

  8. Metrics of a 'mole hole' against the Lobachevsky space background

    International Nuclear Information System (INIS)

    Tentyukov, M.N.

    1994-01-01

    'Classical' mole hole are the Euclidean metrics consisting of two large space regions connected by a throat. They are the instanton solutions of the Einstein equations. It is shown that for existence of mole holes in the general relativity theory it is required the energy-momentum tensor breaking energetic conditions. 9 refs., 7 figs

  9. Complete Hydatidiform Mole Coexisting with a Live Fetus | Ezem ...

    African Journals Online (AJOL)

    Hydatidiform mole co-existing with a normal fetus is very rare. We report a case of a 36 year old woman Para 4+0 who presented with amenorrhoea of twenty four weeks duration, vaginal bleeding , abdominal pain and pre-eclampsia. Ultrasound examination revealed a hydatidiform mole coexisting with a normal living fetus.

  10. Moles: Tool-Assisted Environment Isolation with Closures

    Science.gov (United States)

    de Halleux, Jonathan; Tillmann, Nikolai

    Isolating test cases from environment dependencies is often desirable, as it increases test reliability and reduces test execution time. However, code that calls non-virtual methods or consumes sealed classes is often impossible to test in isolation. Moles is a new lightweight framework which addresses this problem. For any .NET method, Moles allows test-code to provide alternative implementations, given as .NET delegates, for which C# provides very concise syntax while capturing local variables in a closure object. Using code instrumentation, the Moles framework will redirect calls to provided delegates instead of the original methods. The Moles framework is designed to work together with the dynamic symbolic execution tool Pex to enable automated test generation. In a case study, testing code programmed against the Microsoft SharePoint Foundation API, we achieved full code coverage while running tests in isolation without an actual SharePoint server. The Moles framework integrates with .NET and Visual Studio.

  11. Flexible Surface Acoustic Wave Device with AlN Film on Polymer Substrate

    Directory of Open Access Journals (Sweden)

    Jian Zhou

    2012-01-01

    Full Text Available Surface acoustic wave device with c-axis-oriented aluminum nitride (AlN piezoelectric thin films on polymer substrates can be potentially used for development of flexible sensors, flexible microfluidic applications, microsystems, and lab-on-chip systems. In this work, the AlN films have been successfully deposited on polymer substrates using the DC reactive magnetron-sputtering method at room temperature, and the XRD, SEM, and AFM methods reveal that low deposition pressure is beneficial to the highly c-axis-oriented AlN film on polymer substrates. Studies toward the development of AlN thin film-based flexible surface acoustic wave devices on the polymer substrates are initiated and the experimental and simulated results demonstrate the devices showing the acoustic wave velocity of 9000–10000 m/s, which indicate the AlN lamb wave.

  12. Genome Stability Maintenance in Naked Mole-Rat.

    Science.gov (United States)

    Petruseva, I O; Evdokimov, A N; Lavrik, O I

    2017-01-01

    The naked mole-rat ( Heterocephalus glaber ) is one of the most promising models used to study genome maintenance systems, including the effective repair of damage to DNA. The naked mole-rat is the longest lived rodent species, which is extraordinarily resistant to cancer and has a number of other unique phenotypic traits. For at least 80% of its lifespan, this animal shows no signs of aging or any increased likelihood of death and retains the ability to reproduce. The naked mole-rat draws the heightened attention of researchers who study the molecular basis of lengthy lifespan and cancer resistance. Despite the fact that the naked mole-rat lives under genotoxic stress conditions (oxidative, etc.), the main characteristics of its genome and proteome are a high stability and effective functioning. Replicative senescence in the somatic cells of naked mole-rats is missing, while an additional p53/pRb-dependent mechanism of early contact inhibition has been revealed in its fibroblasts, which controls cell proliferation and its mechanism of arf- dependent aging. The unique traits of phenotypic and molecular adaptations found in the naked mole-rat speak to a high stability and effective functioning of the molecular machinery that counteract damage accumulation in its genome. This review analyzes existing results in the study of the molecular basis of longevity and high cancer resistance in naked mole-rats.

  13. Effects of AlN nucleation layers on the growth of AlN films using high temperature hydride vapor phase epitaxy

    International Nuclear Information System (INIS)

    Balaji, M.; Claudel, A.; Fellmann, V.; Gélard, I.; Blanquet, E.; Boichot, R.; Pierret, A.

    2012-01-01

    Highlights: ► Growth of AlN Nucleation layers and its effect on high temperature AlN films quality were investigated. ► AlN nucleation layers stabilizes the epitaxial growth of AlN and improves the surface morphology of AlN films. ► Increasing growth temperature of AlN NLs as well as AlN films improves the structural quality and limits the formation of cracks. - Abstract: AlN layers were grown on c-plane sapphire substrates with AlN nucleation layers (NLs) using high temperature hydride vapor phase epitaxy (HT-HVPE). Insertion of low temperature NLs, as those typically used in MOVPE process, prior to the high temperature AlN (HT-AlN) layers has been investigated. The NLs surface morphology was studied by atomic force microscopy (AFM) and NLs thickness was measured by X-ray reflectivity. Increasing nucleation layer deposition temperature from 650 to 850 °C has been found to promote the growth of c-oriented epitaxial HT-AlN layers instead of polycrystalline layers. The growth of polycrystalline layers has been related to the formation of dis-oriented crystallites. The density of such disoriented crystallites has been found to decrease while increasing NLs deposition temperature. The HT-AlN layers have been characterized by X-ray diffraction θ − 2θ scan and (0 0 0 2) rocking curve measurement, Raman and photoluminescence spectroscopies, AFM and field emission scanning electron microscopy. Increasing the growth temperature of HT-AlN layers from 1200 to 1400 °C using a NL grown at 850 °C improves the structural quality as well as the surface morphology. As a matter of fact, full-width at half-maximum (FWHM) of 0 0 0 2 reflections was improved from 1900 to 864 arcsec for 1200 °C and 1400 °C, respectively. Related RMS roughness also found to decrease from 10 to 5.6 nm.

  14. Growth of high quality AlN films on CVD diamond by RF reactive magnetron sputtering

    Science.gov (United States)

    Chen, Liang-xian; Liu, Hao; Liu, Sheng; Li, Cheng-ming; Wang, Yi-chao; An, Kang; Hua, Chen-yi; Liu, Jin-long; Wei, Jun-jun; Hei, Li-fu; Lv, Fan-xiu

    2018-02-01

    A highly oriented AlN layer has been successfully grown along the c-axis on a polycrystalline chemical vapor deposited (CVD) diamond by RF reactive magnetron sputtering. Structural, morphological and mechanical properties of the heterostructure were investigated by Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM), Transmission Electron Microscopy (TEM), X-ray diffraction (XRD), Nano-indentation and Four-probe meter. A compact AlN film was demonstrated on the diamond layer, showing columnar grains and a low surface roughness of 1.4 nm. TEM results revealed a sharp AlN/diamond interface, which was characterized by the presence of a distinct 10 nm thick buffer layer resulting from the initial AlN growth stage. The FWHM of AlN (002) diffraction peak and its rocking curve are as low as 0.41° and 3.35° respectively, indicating a highly preferred orientation along the c-axis. AlN sputtered films deposited on glass substrates show a higher bulk resistivity (up to 3 × 1012 Ω cm), compared to AlN films deposited on diamond (∼1010 Ω cm). Finally, the film hardness and Young's modulus of AlN films on diamond are 25.8 GPa and 489.5 GPa, respectively.

  15. Spectroellipsometric investigation of optical, morphological, and structural properties of reactively sputtered polycrystalline AlN films

    International Nuclear Information System (INIS)

    Easwarakhanthan, T.; Hussain, S. S.; Pigeat, P.

    2010-01-01

    The optical and morphological properties of reactively sputtered AlN films on Si substrates have been studied in this work from a self-consistent three-layer optical model developed from spectroscopic-ellipsometry analysis and validated by observations from transmission-electron microscopy, Auger electron spectroscopy, and in situ reflectance interferometry. These properties correlate to the film microstructural properties. Accordingly, the almost thickness-independent refractive index of 2.01 of the bulk AlN layer indicates its polycrystalline microstructure. This layer also appears ungraded, homogeneous, isotropic, and free of excess Al, as if grown through a steady process. The small film absorption points to the Urbach tail states produced by the structural disorder typical of such sputtered films. The films' interface layer consists of a graded Bruggeman intermix of outdiffused Si and AlN materials spreading over 10-12 nm thickness. The surface morphology includes an Al 2 O 3 -oxidized outer rough surface gradually becoming AlN bulk with diminishing amounts of Al 2 O 3 and inner pores. The increase in the surface-layer thickness, as the film grows, indicates further surface roughening due to enlarging crystals in a disoriented growth. This spectroscopic-ellipsometry analysis of AlN films has allowed us to study the effect of substrate biasing on the AlN microstructure and to place forward a new processing method for the surface smoothening of rough AlN and diamond films.

  16. Production of AlN films: ion nitriding versus PVD coating

    International Nuclear Information System (INIS)

    Figueroa, U.; Salas, O.; Oseguera, J.

    2004-01-01

    The properties of AlN render this material very attractive for optical, electronic, and tribological applications; thus, a great interest exists for the production of thin AlN films on a variety of substrates. Many methods have been developed for this purpose where two processes stand out: plasma-assisted nitriding (PAN) and PVD coating. In the present paper, we compare the processing advantages and disadvantages of both methods in terms of the characteristics of the layers formed. AlN production by ion nitriding is very sensitive to presputtering cleaning and working pressure. Layers several micrometers thick can be produced in a few hours, which are formed by a fine mixture of Al+AlN. The surface morphology of the layers is rather rough. On the other hand, formation of PVD AlN coatings by DC reactive magnetron sputtering is more readily performed and better controlled than in ion nitriding. PVD results in macroscopically smoother AlN films and with similar thickness than the ion nitrided layers but produced in shorter processing times. The morphology of the PVD AlN layers is columnar with a fairly flat surface. Mechanisms for the formation of both types of AlN layers are proposed. One of the main differences between the two processes that explain the different AlN layer morphologies is the energy of the particles that arrive at the substrate. Considering only the processing advantages and the morphology of the AlN layers formed, PVD performs better than PAN processing

  17. Growth and investigation of TiO2 and AlN nanostructure’s properties

    Directory of Open Access Journals (Sweden)

    A. Bahari

    2008-03-01

    Full Text Available  We have grown TiO2 and AlN under ultra high vacuum and high pressure conditions and studied their structures with using AES and SEM techniques. The obtained results show that an amorphous film of TiO2 and AlN could be formed on silicon substrate. Furthermore, TiO2 and AlN are high – K dielectric materials and they can thus be replaced to ultra thin gate oxide film.

  18. White Noise Responsiveness of an AlN Piezoelectric MEMS Cantilever Vibration Energy Harvester

    International Nuclear Information System (INIS)

    Jia, Y; Seshia, A A

    2014-01-01

    This paper reports the design, analysis and experimental characterisation of a piezoelectric MEMS cantilever vibration energy harvester, the enhancement of its power output by adding various values of end mass, as well as assessing the responsiveness towards white noise. Devices are fabricated using a 0.5 μm AlN on 10 μm doped Si process. Cantilevers with 5 mm length and 2 mm width were tested at either unloaded condition (MC0: f n 577 Hz) or subjected to estimated end masses of 2 mg (MC2: f n 129 Hz) and 5 mg (MC5: f n 80 Hz). While MC0 was able to tolerate a higher drive acceleration prior to saturation (7 g with 0.7 μW), MC5 exhibited higher peak power attainable at a lower input vibration (2.56 μW at 3 ms −2 ). MC5 was also subjected to band-limited (10 Hz to 2 kHz) white noise vibration, where the power response was only a fraction of its resonant counterpart for the same input: peak instantaneous power >1 μW was only attainable beyond 2 g of white noise, whereas single frequency resonant response only required 2.5 ms −2 . Both the first resonant response and the band-limited white noise response were also compared to a numerical model, showing close agreements

  19. A kinetics model for MOCVD deposition of AlN film based on Grove theory

    Science.gov (United States)

    Pu, Kaiwen; Dai, Xianying; Miao, Dongming; Wu, Shujing; Zhao, Tianlong; Hao, Yue

    2017-11-01

    Based on Grove theory, a kinetic model for MOCVD deposition of AlN film was proposed and built in this paper. Physical and chemical processes, e.g., gas phase transport, surface adsorption, surface chemical reactions, as well as the gas phase reactions in boundary layer were analyzed in the kinetic model. Based on this model, the effects of substrate temperature and chamber pressure on the growth rate of AlN film were investigated, as well as the corresponding mechanisms. Meanwhile, the dependences of AlN growth rate and temperature, pressure for three types of reaction pathways were also analyzed. The simulated results provide an important insight into the optimizing of AlN growth with appropriate temperature and pressure in experiment.

  20. First-principles molecular dynamics investigation of thermal and mechanical stability of the TiN(001)/AlN and ZrN(001)/AlN heterostructures

    International Nuclear Information System (INIS)

    Ivashchenko, V.I.; Veprek, S.; Turchi, P.E.A.; Shevchenko, V.I.; Leszczynski, J.; Gorb, L.; Hill, F.

    2014-01-01

    First-principles quantum molecular dynamics investigations of TiN(001)/AlN and ZrN(001)/AlN heterostructures with one and two monolayers (1 ML and 2 ML) of AlN interfacial layers were carried out in the temperature range of 0–1400 K with subsequent static relaxation. It is shown that the epitaxially stabilized cubic B1-AlN interfacial layers are preserved in all TiN(001)/AlN heterostructures over the whole temperature range. In the ZrN(001)/AlN heterostructures, the B1-AlN(001) interfacial layer exists at 0 K, but it transforms into a distorted one at 10 K consisting of tetrahedral AlN 4 , octahedral AlN 6 , and AlN 5 units. The thermal stability of the interfaces was investigated by studying the phonon dynamic stability of the B1-AlN phase with different lattice parameters. The calculations showed that the B1-AlN interface should be unstable in ZrN(001)/AlN heterostructures and nanocomposites, and in those based on transition metal nitrides with lattice parameters larger than 4.4 Å. Electronic band structure calculations showed that energy gap forms around the Fermi energy for all interfaces. The formation of the interfacial AlN layer in TiN and ZrN crystals reduces their ideal tensile and shear strengths. Upon tensile load, decohesion occurs between Ti (Zr) and N atoms adjacent to the 1 ML AlN interfacial layer, whereas in the case of 2 ML AlN it occurs inside the TiN and ZrN slabs. The experimentally reported strength enhancement in the TiN/AlN and ZrN/AlN heterostructures is attributed to impeding effect of the interfacial layer on the plastic flow. - Highlights: • First-principles quantum molecular dynamics studies were conducted. • TiN- and ZrN-based heterostructures with one and two AlN interfacial layers. • Stability and structural transformation between 0 and 1400 K have been calculated. • Stress–strain relationships and ideal strengths determined. • Systems which may form stable superhard heterostructures are identified

  1. Analysis of internal doses to Mole voles inhabiting the East-Ural radioactive trace

    Energy Technology Data Exchange (ETDEWEB)

    Malinovsky, G.; Yarmoshenko, I. [Institute of Industrial Ecology UB RAS (Russian Federation); Chibiryak, M.; Vasil' ev, A. [Institute of Plant and Animal Ecology UB RAS (Russian Federation)

    2014-07-01

    absorbed fractions of beta-radiation energy for different combinations of source and target organs calculated using voxel-based mouse model (e.g. Stabin et. al., 2006). Distribution of radionuclide by organs and tissues was estimated applying developed strontium biokinetic model for mouse-like rodent. Similar approach can be used to calculate radiation doses to organs and tissues of mole voles, taking into account differences in size and body weight of mice and mole voles. Strontium biokinetic model for mole vole can be designed basing on that of mouse-like rodent, considering physiological differences and available published data on strontium retention in the organism of burrowing rodents. There are no specific voxel-based models of mole vole. Nevertheless, the models of small mammals of similar size can be applied. Assessment of individual doses to mole voles allows investigating the relationship between radiation dose to these animals and observed morphometric and other biological effects. Document available in abstract form only. The research has been made under support of Ural Branch of Russian Academy of Sciences, project 12-M-24-2016. (authors)

  2. Optical constants and polarimetric properties of AlN thin films

    Science.gov (United States)

    Ushenko, Yu. A.; Maryanchuk, P. D.; Solovan, M. M.; Pidkamin, L. J.; Brus, V. V.

    2018-01-01

    The results of an experimental study of the polarization characteristics of thin films based on aluminum nitride (AlN) are presented. It was found that an increase in the partial pressure of nitrogen (with the appropriate technology for producing the AlN film) leads to a substantial increase in the absorptivity of the film itself and a decrease in its linear dichroism parameter.

  3. Surface passivation of GaAs nanowires by the atomic layer deposition of AlN

    Energy Technology Data Exchange (ETDEWEB)

    Shtrom, I. V., E-mail: igorstrohm@mail.ru; Bouravleuv, A. D. [Russian Academy of Sciences, Ioffe Physical–Technical Institute (Russian Federation); Samsonenko, Yu. B.; Khrebtov, A. I. [Russian Academy of Sciences, St. Petersburg National Research Academic University—Nanotechnology Research and Education Center (Russian Federation); Soshnikov, I. P. [Russian Academy of Sciences, Ioffe Physical–Technical Institute (Russian Federation); Reznik, R. R.; Cirlin, G. E., E-mail: cirlin@beam.ioffe.ru [Russian Academy of Sciences, St. Petersburg National Research Academic University—Nanotechnology Research and Education Center (Russian Federation); Dhaka, V.; Perros, A.; Lipsanen, H. [Aalto University (Finland)

    2016-12-15

    It is shown that the atomic layer deposition of thin AlN layers can be used to passivate the surface states of GaAs nanowires synthesized by molecular-beam epitaxy. Studies of the optical properties of samples by low-temperature photoluminescence measurements shows that the photoluminescence-signal intensity can be increased by a factor of up to five by passivating the nanowires with a 25-Å-thick AlN layer.

  4. Flexible-CMOS and biocompatible piezoelectric AlN material for MEMS applications

    International Nuclear Information System (INIS)

    Jackson, Nathan; Keeney, Lynette; Mathewson, Alan

    2013-01-01

    The development of a CMOS compatible flexible piezoelectric material is desired for numerous applications and in particular for biomedical MEMS devices. Aluminum nitride (AlN) is the most commonly used CMOS compatible piezoelectric material, which is typically deposited on Si in order to enhance the c-axis (002) crystal orientation which gives AlN its high piezoelectric properties. This paper reports on the successful deposition of AlN on polyimide (PI-2611) material. The AlN deposited has a FWHM (002) value of 5.1° and a piezoelectric d 33 value of 1.12 pm V −1 , and SEM images show high quality columnar grains. The highly crystalline AlN material is due to the semi-crystalline properties of the polyimide film used. Cytotoxicity testing showed the AlN/polyimide material to be non-toxic to 3T3 cells and primary neurons. Surface properties of the AlN/polyimide film were evaluated as they have a significant effect on the adhesion of cells to the film. The results show neurons adhering to the AlN surface. The results of this paper show the characterization of a new flexible-CMOS and biocompatible AlN/polyimide material for MEMS devices with improved crystallinity and piezoelectric properties. (paper)

  5. Controlled Growth of Conductive AlN Thin Films by Plasma-Assisted Reactive Evaporation

    Science.gov (United States)

    Alizadeh, M.; Goh, B. T.; Rahman, S. A.

    2017-07-01

    In this work, the growth of conductive AlN thin films by plasma-assisted reactive evaporation at different filament-to-substrate distances was presented and discussed. The elemental composition, surface morphology, structural, optical, and electrical properties of the films were examined by energy-dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy, grazing incidence X-ray diffraction (GIXRD), Fourier transform infrared spectroscopy (FTIR), optical measurement, and current-voltage ( I- V) characterizations. The electrical study revealed that the films are conductive, as ohmic conductivity was observed from I- V results. The GIXRD results of AlN thin films showed that by decreasing the distance, the intensity of the peak corresponding to metallic Al decreases while that of AlN increases. EDX and XPS results indicated that at shorter distances, the incorporation of N into the AlN films is enhanced. This was further confirmed by FTIR results, which showed that the incorporation of Al-N bonds in the grown AlN films was enhanced by decreasing the distance. It was shown that the optical absorption edge of the grown films shifts from the near-ultraviolet (UV) region to far-UV as the distance is decreased.

  6. Electron absorbed fractions in skeletal soft tissues based on red bone marrow segmentation at runtime in muCT images of human trabecular bone;Fracoes absorvidas de eletrons em tecidos moles do esqueleto avaliadas com base na segmentacao em tempo de execucao da medula ossea vermelha contida em imagens muCT do osso trabecular humano

    Energy Technology Data Exchange (ETDEWEB)

    Vieira, J.W. [Instituto Federal de Educacao, Ciencia e Tecnologia de Pernambuco, Recife, PE (Brazil); Kramer, R. [Universidade de Pernambuco (UPE), Recife, PE (Brazil). Escola Politecnica; Khoury, H.J. [Universidade Federal de Pernambuco (UFPE), Recife, PE (Brazil). Dept. de Energia Nuclear; Robson-Brown, K. [University of Bristol, Bristol (United Kingdom). Dept. of Archaeology and Anthropology

    2009-07-01

    Skeletal dosimetry determines equivalent dose or absorbed fractions in the red bone marrow (RBM) and the osteogenic cells on bone surfaces (BSC). Following a method used earlier for the BSC, RBM and yellow bone marrow (YBM) have been segmented in the marrow cavities of muCT images of human spongiosa at runtime, i.e. during the execution of the Monte Carlo calculation, which avoids the necessity to segment RBM and YBM externally in muCT images for many different cellularities and to store the data. Using this internal RBM/YBM segmentation, this study presents electron absorbed fractions for the RBM and the BSC as a function of the voxel resolution and also compares the results with data from other investigations. (author)

  7. A cytosolic protein factor from the naked mole-rat activates proteasomes of other species and protects these from inhibition

    Science.gov (United States)

    Rodriguez, Karl A.; Osmulski, Pawel A.; Pierce, Anson; Weintraub, Susan T.; Gaczynska, Maria; Buffenstein, Rochelle

    2015-01-01

    The naked mole-rat maintains robust proteostasis and high levels of proteasome-mediated proteolysis for most of its exceptional (~31y) life span. Here, we report that the highly active proteasome from the naked mole-rat liver resists attenuation by a diverse suite of proteasome-specific small molecule inhibitors. Moreover, mouse, human, and yeast proteasomes exposed to the proteasome-depleted, naked mole-rat cytosolic fractions, recapitulate the observed inhibition resistance, and mammalian proteasomes also show increased activity. Gel filtration coupled with mass spectrometry and atomic force microscopy indicates that these traits are supported by a protein factor that resides in the cytosol. This factor interacts with the proteasome and modulates its activity. Although HSP72 and HSP40 (Hdj1) are among the constituents of this factor, the observed phenomenon, such as increasing peptidase activity and protecting against inhibition cannot be reconciled with any known chaperone functions. This novel function may contribute to the exceptional protein homeostasis in the naked mole-rat and allow it to successfully defy aging. PMID:25018089

  8. Ultrasonographic findings of Myoma, H-mole and Missed abortion

    International Nuclear Information System (INIS)

    Huh, Nam Yoon; You, H. S.; Seong, K. J.; Park, C. Y.

    1982-01-01

    Ultrasonography is very important in the diagnosis of various kinds of diseases in Obsterics and Gynecology. It has high diagnostic accuracy in the diagnosis of pelvic masses and widely used for the detection of normal orpathologic pregnancy. But still it is difficult to differentiate degenerated myoma, H-mole and missed abortion by ultrasonography. So the authors analyzed the ultrasonographic findings of 81 patients with myoma(29 cases), H-mole(23 cases), and missed abortion(29 cases) and the results are as follows; 1. Diagnostic accuracy was 8.6% in myoma, 87% in H-mole and 89% in missed abortion. 2. The most typical ultrasonographic finding of myoma was obulated mass contour with nonhomogenous internal echo. 3. The most characteristic finding of H-mole was fine vesicular pattern internal echo with globular enlargement of uterus. 4. The most frequent finding of missed abortion was deformed gestational sac with or without remained fetal echo. 5. Clinical correlation was very important for accurate diagnosis, especially when differential diagnosis was very difficult between myoma with marked cystic degeneration, missed abortion with large distorted gestational sac and H-mole with severe degeneration

  9. Case report: nephrotic syndrome associated with a total hydatidiform mole.

    Science.gov (United States)

    Komatsuda, A; Nakamoto, Y; Asakura, K; Yasuda, T; Imai, H; Miura, A B

    1992-05-01

    The authors describe a 51-year-old Japanese woman who developed nephrotic syndrome in association with a total hydatidiform mole. The nephrotic syndrome remitted completely following hysterectomy. A renal biopsy performed before the operation showed diffuse mesangial cell proliferation of a moderate degree, and thickened capillary walls with focal and segmental subendothelial deposits, as well as circumferential mesangial interposition. Occasional foci of the mesangiolysis were also observed. Immunofluorescence microscopy revealed granular staining of IgM along the glomerular capillary walls in a fringe pattern. A review of the literature revealed that this patient appears to be the first case of nephrotic syndrome associated with a total mole, although there have been two cases of nephrotic syndrome due to preeclamptic nephropathy associated with a partial or transitional mole.

  10. A case of nephrotic syndrome associated with hydatiform mole

    Directory of Open Access Journals (Sweden)

    Tarlan Hamidehkhou

    2010-12-01

    Full Text Available The present case study is on a 16-year-old woman who was suffering from nephritic syndrome after recovery from complete type of hydatiform mole. She admitted in hospital because of proteinurea and hematuria. In her past medical history she had a suction curettage for hydatiform mole. After she received 4 courses chemotherapy, she completely recovered and βhCG has fallen from 1980 IU/L to under 10 IU/mL. Then she showed generalized edema, proteinurea and hematuria compatible with nephritic syndrome. After six courses chemotherapy the symptoms of nephrotic syndrome and invasive mole diminished, she released from hospital and scheduled for follow-up.

  11. A case of nephrotic syndrome associated with hydatiform mole.

    Science.gov (United States)

    Mohammadjafari, Razieh; Abedi, Parvin; Belady, Syfolah; Hamidehkho, Tarlan; Razi, Taghi

    2010-12-31

    The present case study is on a 16-year-old woman who was suffering from nephrotic syndrome after recovery from complete type of hydatiform mole. She was admitted in hospital because of proteinurea and hematuria. Then she was showing a generalized edema compatible with neprhotic syndrome. In her past medical history she had a suction curettage for hydatiform mole. After she received 4 courses chemotherapy, she completely recovered and βhCG has fallen from 12127 IU/L to under 10 IU/mL. Then she showed generalized edema, proteinurea and hematuria compatible with nephritic syndrome. After six courses chemotherapy the symptoms of nephrotic syndrome and invasive mole diminished, she released from hospital and scheduled for follow-up.

  12. Potential acute effects of suspended aluminum nitride (AlN) nanoparticles on soluble microbial products (SMP) of activated sludge.

    Science.gov (United States)

    Zhou, Lijie; Zhuang, Weiqin; Wang, Xin; Yu, Ke; Yang, Shufang; Xia, Siqing

    2017-07-01

    The study aims to identify the potential acute effects of suspended aluminum nitride (AlN) nanoparticles (NPs) on soluble microbial products (SMP) of activated sludge. Cultured activated sludge loaded with 1, 10, 50, 100, 150 and 200mg/L of AlN NPs were carried out in this study. As results showed, AlN NPs had a highly inverse proportionality to bacterial dehydrogenase and OUR, indicating its direct toxicity to the activated sludge viability. The toxicity of AlN NPs was mainly due to the nano-scale of AlN NPs. In SMP, AlN NPs led to the decrease of polysaccharide and humic compounds, but had slight effects on protein. The decrease of tryptophan-like substances in SMP indicated the inhibition of AlN NPs on the bacterial metabolism. Additionally, AlN NPs reduced obviously the molecular weight of SMP, which might be due to the nano-scale of AlN. Copyright © 2017. Published by Elsevier B.V.

  13. Extreme hypoxia tolerance of naked mole-rat brain.

    Science.gov (United States)

    Larson, John; Park, Thomas J

    2009-12-09

    Mammalian brains have extremely high levels of aerobic metabolism and typically suffer irreversible damage after brief periods of oxygen deprivation such as occur during stroke or cardiac arrest. Here we report that brain tissue from naked mole-rats, rodents that live in a chronically low-oxygen environment, is remarkably resistant to hypoxia: naked mole-rat neurons maintain synaptic transmission much longer than mouse neurons and can recover from periods of anoxia exceeding 30 min. We suggest that brain tolerance to hypoxia may result from slowed or arrested brain development in these extremely long-lived animals.

  14. Valence and conduction band offsets of β-Ga2O3/AlN heterojunction

    KAUST Repository

    Sun, Haiding

    2017-10-16

    Both β-Ga2O3 and wurtzite AlN have wide bandgaps of 4.5–4.9 and 6.1 eV, respectively. We calculated the in-plane lattice mismatch between the (−201) plane of β-Ga2O3 and the (0002) plane of AlN, which was found to be 2.4%. This is the smallest mismatch between β-Ga2O3 and binary III-nitrides which is beneficial for the formation of a high quality β-Ga2O3/AlN heterojunction. However, the valence and conduction band offsets (VBO and CBO) at the β-Ga2O3/AlN heterojunction have not yet been identified. In this study, a very thin (less than 2 nm) β-Ga2O3 layer was deposited on an AlN/sapphire template to form the heterojunction by pulsed laser deposition. High-resolution X-ray photoelectron spectroscopy revealed the core-level (CL) binding energies of Ga 3d and Al 2p with respect to the valence band maximum in individual β-Ga2O3 and AlN layers, respectively. The separation between Ga 3d and Al 2p CLs at the β-Ga2O3/AlN interface was also measured. Eventually, the VBO was found to be −0.55 ± 0.05 eV. Consequently, a staggered-gap (type II) heterojunction with a CBO of −1.75 ± 0.05 eV was determined. The identification of the band alignment of the β-Ga2O3/AlN heterojunction could facilitate the design of optical and electronic devices based on these and related alloys.

  15. AlN film deposition as a semiconductor device

    Directory of Open Access Journals (Sweden)

    Julio Cesar Caicedo

    2013-05-01

    Full Text Available AlN films were deposited by pulsed laser deposition (PLD using an Nd: YAG laser (λ = 1064 nm. The films were deposited in a nitrogen atmosphere as working gas; the cathode was an aluminium high purity (99.99% target. The films were deposited using 7 J/cm2 laser fluence for 10 minutes on silicon (100 substrates. The working pressure was 9x10-3 mbar and the substrate temperature was varied from 200°C to 630°C. The thickness measured by profilometer was 150 nm for all films. Moreover, surface acoustic wave (SAW devices with a Mo/AlN/Si configuration have been fabricated using AlN-buffer and Mo Channel. The films’ morphology and composition were studied using scanning electron microscopy (SEM and energy dispersive X-ray analysis (EDX, respectively. The films’ optical reflectance spectra and colour coordinates were obtained by optical spectral reflectometry in the 400-900 cm-1 range using an Ocean Optics 2000 spectrophotometer. The present work found clear dependence on morphological properties, reflectance, dominant wavelength colour purity, frequency response and acoustic wave speed in terms of the temperature applied to the substrate. About 30% reduction in reflectance was observed and increased acoustic wave speed of about 1.3 % when the temperature was increased from 200°C to 630°C.

  16. Structure design of AlN double-ended tuning fork resonators

    Science.gov (United States)

    Lei, Qiang; Gao, Yang; Han, Chao

    2017-11-01

    The resonant sensors based on aluminum nitride double-ended tuning fork (AlN DETF) have the characteristics of small size, good stability and reliability, fast response. In order to improve the sensitivity and resolution, it is necessary to analyze the influence of the structure parameters of vibrating beam on the sensitivity and signal power of AlN resonator. The multi-physics model of AlN DETF resonator was established to verify effect of single parameter on the sensitivity by pre-stressed eigenfrequency analysis. The relationships between signal power and length, width of vibrating beam were obtained by post-processing data of simulation results when the thickness remained constant. The results show that relative sensitivity and signal power are growing with opposite direction with the width or the length of the beam. Therefore, there is a design tradeoff between signal power and relative sensitivity of AlN resonator according to the process and structure strength. The optimized AlN DETF resonator was simulated, its sensitivity, signal power and Q are 56 Hz/μN, 6.8e-4 nW and 958, respectively.

  17. Understanding AlN Obtaining Through Computational Thermodynamics Combined with Experimental Investigation

    Science.gov (United States)

    Florea, R. M.

    2017-06-01

    Basic material concept, technology and some results of studies on aluminum matrix composite with dispersive aluminum nitride reinforcement was shown. Studied composites were manufactured by „in situ” technique. Aluminum nitride (AlN) has attracted large interest recently, because of its high thermal conductivity, good dielectric properties, high flexural strength, thermal expansion coefficient matches that of Si and its non-toxic nature, as a suitable material for hybrid integrated circuit substrates. AlMg alloys are the best matrix for AlN obtaining. Al2O3-AlMg, AlN-Al2O3, and AlN-AlMg binary diagrams were thermodynamically modelled. The obtained Gibbs free energies of components, solution parameters and stoichiometric phases were used to build a thermodynamic database of AlN- Al2O3-AlMg system. Obtaining of AlN with Liquid-phase of AlMg as matrix has been studied and compared with the thermodynamic results. The secondary phase microstructure has a significant effect on the final thermal conductivity of the obtained AlN. Thermodynamic modelling of AlN-Al2O3-AlMg system provided an important basis for understanding the obtaining behavior and interpreting the experimental results.

  18. Additional material of the enigmatic golden mole Cryptochloris zyli ...

    African Journals Online (AJOL)

    Van Zyl's golden mole (Cryptochloris zyli) is a distinctive but little-known species from the northwestern Cape Province of South Africa. Many authors have mentioned that it is known only by the holotype. Two other specimens are now known to exist; one was discovered in the Museum of Comparative Zoology at Harvard ...

  19. Hydatidiform moles among patients with incomplete abortion in ...

    African Journals Online (AJOL)

    Background: Prevalence of hydatidiform mole is not clearly defined, partly because most studies have reported different prevalence rates from different regions. However, there is no previous study that has determined the prevalence and associated risk factors of HM among patients with incomplete abortion evacuated at ...

  20. Burrow architecture of the Damaraland mole-rat ( Fukomys ...

    African Journals Online (AJOL)

    The burrow architecture (length, internal dimensions, fractal dimension of tunnel systems, number of nesting chambers and surface mounds) was investigated in the Damaraland mole-rat (Fukomys damarensis). A total of 31 animals were caught from five different colonies and their burrow systems were excavated in their ...

  1. First-principles molecular dynamics investigation of thermal and mechanical stability of the TiN(001)/AlN and ZrN(001)/AlN heterostructures

    Energy Technology Data Exchange (ETDEWEB)

    Ivashchenko, V.I., E-mail: ivash@ipms.kiev.ua [Institute of Problems of Material Science, National Academy of Science of Ukraine, Krzhyzhanosky str. 3, 03142 Kyiv (Ukraine); Veprek, S., E-mail: stan.veprek@lrz.tum.de [Department of Chemistry, Technical University Munich, Lichtenbergstrasse 4, D-85747 Garching (Germany); Turchi, P.E.A. [Lawrence Livermore National Laboratory (L-352), P.O. Box 808, Livermore, CA 94551 (United States); Shevchenko, V.I. [Institute of Problems of Material Science, National Academy of Science of Ukraine, Krzhyzhanosky str. 3, 03142 Kyiv (Ukraine); Leszczynski, J. [Department of Chemistry and Biochemistry, Interdisciplinary Center for Nanotoxicity, Jackson State University, Jackson, MS 39217 (United States); Gorb, L. [Department of Chemistry and Biochemistry, Interdisciplinary Center for Nanotoxicity, Jackson State University, Jackson, MS 39217 (United States); U.S. Army ERDC, Vicksburg, MS 39180 (United States); Hill, F. [U.S. Army ERDC, Vicksburg, MS 39180 (United States)

    2014-08-01

    First-principles quantum molecular dynamics investigations of TiN(001)/AlN and ZrN(001)/AlN heterostructures with one and two monolayers (1 ML and 2 ML) of AlN interfacial layers were carried out in the temperature range of 0–1400 K with subsequent static relaxation. It is shown that the epitaxially stabilized cubic B1-AlN interfacial layers are preserved in all TiN(001)/AlN heterostructures over the whole temperature range. In the ZrN(001)/AlN heterostructures, the B1-AlN(001) interfacial layer exists at 0 K, but it transforms into a distorted one at 10 K consisting of tetrahedral AlN{sub 4}, octahedral AlN{sub 6}, and AlN{sub 5} units. The thermal stability of the interfaces was investigated by studying the phonon dynamic stability of the B1-AlN phase with different lattice parameters. The calculations showed that the B1-AlN interface should be unstable in ZrN(001)/AlN heterostructures and nanocomposites, and in those based on transition metal nitrides with lattice parameters larger than 4.4 Å. Electronic band structure calculations showed that energy gap forms around the Fermi energy for all interfaces. The formation of the interfacial AlN layer in TiN and ZrN crystals reduces their ideal tensile and shear strengths. Upon tensile load, decohesion occurs between Ti (Zr) and N atoms adjacent to the 1 ML AlN interfacial layer, whereas in the case of 2 ML AlN it occurs inside the TiN and ZrN slabs. The experimentally reported strength enhancement in the TiN/AlN and ZrN/AlN heterostructures is attributed to impeding effect of the interfacial layer on the plastic flow. - Highlights: • First-principles quantum molecular dynamics studies were conducted. • TiN- and ZrN-based heterostructures with one and two AlN interfacial layers. • Stability and structural transformation between 0 and 1400 K have been calculated. • Stress–strain relationships and ideal strengths determined. • Systems which may form stable superhard heterostructures are identified.

  2. A novel surface micromachining process to fabricate AlN unimorph suspensions and its application for RF resonators

    NARCIS (Netherlands)

    Saravanan, S.; Saravanan, S.; Berenschot, Johan W.; Krijnen, Gijsbertus J.M.; Elwenspoek, Michael Curt

    2006-01-01

    A novel surface micromachining process is reported for aluminum nitride (AlN) thin films to fabricate piezoelectric unimorph suspension devices for micro actuator applications. Wet anisotropic etching of AlN thin film is used with a Cr metal mask layer in the microfabrication process. Tetra methyl

  3. In situ diffraction study on decomposition of Ti2AlN at 1500-1800 deg. C in vacuum

    International Nuclear Information System (INIS)

    Pang, W.K.; Low, I.M.; Kennedy, S.J.; Smith, R.I.

    2010-01-01

    Research highlights: → Ti 2 AlN decomposes to TiN in vacuum at elevated temperature. → Formation of Ti 4 AlN 3 during annealing of Ti 2 AlN at 1600 deg. C. → Study of Avrami kinetics of decomposition in Ti 2 AlN.→ In-situ neutron diffraction study. - Abstract: The susceptibility of Ti 2 AlN to thermal dissociation at 1500-1800 deg. C in high-vacuum has been studied using in situ neutron diffraction. Above 1500 deg. C, Ti 2 AlN decomposed to TiN x primarily through the sublimation of aluminium (Al). The kinetics of isothermal phase decomposition at 1550 deg. C was modelled using a modified Avrami equation. An Avrami exponent (n) of 0.338 was determined, indicative of the highly restricted out-diffusion of Al between the channels of Ti 6 N octahedra. The characteristics of thermal stability and phase transition in Ti 2 AlN are discussed. Characterisation of surface compositions and examination of cross-sectional microstructures of decomposed Ti 2 AlN, using synchrotron radiation diffraction and SEM, respectively, verify the findings of the neutron diffraction; that Ti 2 AlN decomposes to TiN x at the surface primarily via the sublimation of Al from grain boundaries.

  4. DFT study on the adsorption behavior and electronic response of AlN nanotube and nanocage toward toxic halothane gas

    Science.gov (United States)

    Mohammadi, R.; Hosseinian, A.; Khosroshahi, E. Saedi; Edjlali, L.; Vessally, E.

    2018-04-01

    We have investigated the adsorption of a halothane molecule on the AlN nanotube, and nanocage using density functional theory calculations. We predicted that the halothane molecule tends to be physically adsorbed on the surface of AlN nanotube with adsorption energy (Ead) of -4.2 kcal/mol. The electronic properties of AlN nanotube are not affected by the halothane, and it is not a sensor. But the AlN nanocage is more reactive than the AlN nanotube because of its higher curvature. The halothane tends to be adsorbed on a hexagonal ring, an Alsbnd N bond, and a tetragonal ring of the AlN nanocage. The adsorption ability order is as follows: tetragonal ring (Ead = -14.7 kcal/mol) > Alsbnd N bond (Ead = -12.3 kcal/mol) > hexagonal ring (Ead = -10.1 kcal/mol). When a halothane molecule is adsorbed on the AlN nanocage, its electrical conductivity is increased, demonstrating that it can yield an electronic signal at the presence of this molecule, and can be employed in chemical sensors. The AlN nanocage benefits from a short recovery time of about 58 ms at room temperature.

  5. Preliminary comparison of three processes of AlN oxidation: dry, wet and mixed ones

    Directory of Open Access Journals (Sweden)

    Korbutowicz R.

    2016-03-01

    Full Text Available Three methods of AlN layers oxidation: dry, wet and mixed (wet with oxygen were compared. Some physical parameters of oxidized thin films of aluminum nitride (AlN layers grown on silicon Si(1 1 1 were investigated by means Energy-Dispersive X-ray Spectroscopy (EDS and Spectroscopic Ellipsometry (SE. Three series of the thermal oxidations processes were carried out at 1012 °C in pure nitrogen as carrying gas and various gas ambients: (a dry oxidation with oxygen, (b wet oxidation with water steam and (c mixed atmosphere with various process times. All the research methods have shown that along with the rising of the oxidation time, AlN layer across the aluminum oxide nitride transforms to aluminum oxide. The mixed oxidation was a faster method than the dry or wet ones.

  6. Oxidation behaviour of a Ti2AlN MAX-phase coating

    International Nuclear Information System (INIS)

    Wang Qimin; Kim, Kwangho; Garkas, W; Renteria, A Flores; Leyens, C; Sun Chao

    2011-01-01

    In this paper, we reported the oxidation behaviour of Ti 2 AlN coatings on a -TiAl substrate. The coatings composed mainly of Ti 2 AlN MAX phase were obtained by magnetron sputtering and subsequent vacuum annealing. Isothermal oxidation tests at 700-900 deg. C were performed in air. The results indicated that the oxidation resistance of the -TiAl alloy can be improved by depositing a Ti 2 AlN layer on the alloy surface, especially at high temperatures. An Al-rich oxide scale formed on the coating surfaces during oxidation. This scale acts as diffusion barrier blocking the ingress of oxidation, and effectively protects the coated alloys from further oxidation attack.

  7. Oxidation behaviour of a Ti{sub 2}AlN MAX-phase coating

    Energy Technology Data Exchange (ETDEWEB)

    Wang Qimin; Kim, Kwangho [National Core Research Center for Hybrid Materials Solution, Pusan National University, Busan 609-735 (Korea, Republic of); Garkas, W; Renteria, A Flores [Chair of Physical Metallurgy and Materials Technology, Technical University of Brandenburg at Cottbus, 03046 Cottbus (Germany); Leyens, C [Institute of Materials Science, Technical University of Dresden, Helmholtzstrasse 7, 01069 Dresden (Germany); Sun Chao, E-mail: qmwang@pusan.ac.kr, E-mail: kwhokim@pusan.ac.kr [Division of Surface Engineering of Materials, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016 (China)

    2011-10-29

    In this paper, we reported the oxidation behaviour of Ti{sub 2}AlN coatings on a -TiAl substrate. The coatings composed mainly of Ti{sub 2}AlN MAX phase were obtained by magnetron sputtering and subsequent vacuum annealing. Isothermal oxidation tests at 700-900 deg. C were performed in air. The results indicated that the oxidation resistance of the -TiAl alloy can be improved by depositing a Ti{sub 2}AlN layer on the alloy surface, especially at high temperatures. An Al-rich oxide scale formed on the coating surfaces during oxidation. This scale acts as diffusion barrier blocking the ingress of oxidation, and effectively protects the coated alloys from further oxidation attack.

  8. Quantitative Evaluation of Strain in Epitaxial 2H AlN Layers

    International Nuclear Information System (INIS)

    Nader, N.; Pezoldt, J.

    2011-01-01

    To improve the quality of AlN layer deposit on SiC/Si, different Ge amounts (0.25, 0.5, 1, 2ML) were deposited before the carbonization process at the silicon substrate in order to reduce the lattice parameters mismatch between Si and SiC grown layers. The residual stress of the hexagonal AlN layers derives from the phonon frequency shifts of the E1(TO) phonon mode. The crystalline quality of the AlN layer is correlated to and investigated by the full width of the half maximum (FWHM) and the intensity of E1(TO) mode of the 2H-AlN. Best crystalline quality and lower stress value are found in the case where 1ML of Ge amount is predeposited. The E1(TO) mode phonon frequency shifts-down by 3 cm-1/GPa with respect to an unstrained layer. (author)

  9. Sharp bound and free exciton lines from homoepitaxial AlN

    Energy Technology Data Exchange (ETDEWEB)

    Feneberg, Martin [Institut fuer Experimentelle Physik, Abteilung Materialphysik, Otto-von-Guericke-Universitaet Magdeburg (Germany); Institut fuer Quantenmaterie/Gruppe Halbleiterphysik, Universitaet Ulm (Germany); Neuschl, Benjamin; Thonke, Klaus [Institut fuer Quantenmaterie/Gruppe Halbleiterphysik, Universitaet Ulm (Germany); Collazo, Ramon; Rice, Anthony [Department of Materials Science and Engineering, North Carolina State University, Raleigh, NC (United States); Sitar, Zlatko [Department of Materials Science and Engineering, North Carolina State University, Raleigh, NC (United States); HexaTech, Inc., Morrisville, NC (United States); Dalmau, Rafael; Xie, Jinqiao; Mita, Seiji [HexaTech, Inc., Morrisville, NC (United States); Goldhahn, Ruediger [Institut fuer Experimentelle Physik, Abteilung Materialphysik, Otto-von-Guericke-Universitaet Magdeburg (Germany)

    2011-07-15

    MOCVD AlN layers grown in c-direction on PVT bulk AlN substrates are investigated by high-resolution photoluminescence in the energy region of the band gap. The experiments allow for observation of different donor bound exciton lines with a full width at half maximum below 0.5 meV. Assignments are suggested for the substitutional shallow donors silicon and oxygen. The visibility of an excited state of the free exciton with a hole from the highest valence band allows to determine the exciton binding energy to 52.4 meV by use of a simple hydrogen model. The resulting band gap energy is 6.094 eV at 10 K. Comparison with earlier reports on homoepitaxial AlN leads to a new identification of the bands reported there. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  10. Cardiac function of the naked mole-rat: ecophysiological responses to working underground.

    Science.gov (United States)

    Grimes, Kelly M; Voorhees, Andrew; Chiao, Ying Ann; Han, Hai-Chao; Lindsey, Merry L; Buffenstein, Rochelle

    2014-03-01

    The naked mole-rat (NMR) is a strictly subterranean rodent with a low resting metabolic rate. Nevertheless, it can greatly increase its metabolic activity to meet the high energetic demands associated with digging through compacted soils in its xeric natural habitat where food is patchily distributed. We hypothesized that the NMR heart would naturally have low basal function and exhibit a large cardiac reserve, thereby mirroring the species' low basal metabolism and large metabolic scope. Echocardiography showed that young (2-4 yr old) healthy NMRs have low fractional shortening (28 ± 2%), ejection fraction (43 ± 2%), and cardiac output (6.5 ± 0.4 ml/min), indicating low basal cardiac function. Histology revealed large NMR cardiomyocyte cross-sectional area (216 ± 10 μm(2)) and cardiac collagen deposition of 2.2 ± 0.4%. Neither of these histomorphometric traits was considered pathological, since biaxial tensile testing showed no increase in passive ventricular stiffness. NMR cardiomyocyte fibers showed a low degree of rotation, contributing to the observed low NMR cardiac contractility. Interestingly, when the exercise mimetic dobutamine (3 μg/g ip) was administered, NMRs showed pronounced increases in fractional shortening, ejection fraction, cardiac output, and stroke volume, indicating an increased cardiac reserve. The relatively low basal cardiac function and enhanced cardiac reserve of NMRs are likely to be ecophysiological adaptations to life in an energetically taxing environment.

  11. Low oxidation state aluminum-containing cluster anions: Cp∗AlnH-, n = 1-3

    Science.gov (United States)

    Zhang, Xinxing; Ganteför, Gerd; Eichhorn, Bryan; Mayo, Dennis; Sawyer, William H.; Gill, Ann F.; Kandalam, Anil K.; Schnöckel, Hansgeorg; Bowen, Kit

    2016-08-01

    Three new, low oxidation state, aluminum-containing cluster anions, Cp*AlnH-, n = 1-3, were prepared via reactions between aluminum hydride cluster anions, AlnHm-, and Cp*H ligands. These were characterized by mass spectrometry, anion photoelectron spectroscopy, and density functional theory based calculations. Agreement between the experimentally and theoretically determined vertical detachment energies and adiabatic detachment energies validated the computed geometrical structures. Reactions between aluminum hydride cluster anions and ligands provide a new avenue for discovering low oxidation state, ligated aluminum clusters.

  12. Polarity Control and Growth of Lateral Polarity Structures in AlN

    Science.gov (United States)

    2013-05-10

    AlN, lateral polar structures, metal organic chemical vapor deposition Ronny Kirste, Seiji Mita , Lindsay Hussey, Marc Hoffmann, Wei Guo, Isaac Bryan...structures in AlN Ronny Kirste,1 Seiji Mita ,2 Lindsay Hussey,1 Marc P. Hoffmann,1 Wei Guo,1 Isaac Bryan,1 Zachary Bryan,1 James Tweedie,1 Jinqiao Xie,2...and H. X. Jiang, Appl. Phys. Lett. 89(21), 213510–213513 (2006). 2N. Dietz, M. Alevli, R. Atalay, G. Durkaya, R. Collazo, J. Tweedie, S. Mita , and Z

  13. Social status and sex effects on neural morphology in Damaraland mole-rats, Fukomys damarensis.

    Science.gov (United States)

    Anyan, Jeff J; Seney, Marianne L; Holley, Amanda; Bengston, Lynn; Goldman, Bruce D; Forger, Nancy G; Holmes, Melissa M

    2011-01-01

    We previously reported that in a eusocial rodent, the naked mole-rat (Heterocephalus glaber), traditional neural sex differences were absent; instead, neural dimorphisms were associated with breeding status. Here we examined the same neural regions previously studied in naked mole-rats in a second eusocial species, the Damaraland mole-rat (Fukomys damarensis). Damaraland mole-rats live in social groups with breeding restricted to a small number of animals. However, colony sizes are much smaller in Damaraland mole-rats than in naked mole-rats and there is consequently less reproductive skew. In this sense, Damaraland mole-rats may be considered intermediate in social organization between naked mole-rats and more traditional laboratory rodents. We report that, as in naked mole-rats, breeding Damaraland mole-rats have larger volumes of the principal nucleus of the bed nucleus of the stria terminalis and paraventricular nucleus of the hypothalamus than do subordinates, with no effect of sex on these measures. Thus, these structures may play special roles in breeders of eusocial species. However, in contrast to what was seen in naked mole-rats, we also found sex differences in Damaraland mole-rats: volume of the medial amygdala and motoneuron number in Onuf's nucleus were both greater in males than in females, with no significant effect of breeding status. Thus, both sex and breeding status influence neural morphology in Damaraland mole-rats. These findings are in accord with the observed sex differences in body weight and genitalia in Damaraland but not naked mole-rats. We hypothesize that the increased sexual dimorphism in Damaraland mole-rats relative to naked mole-rats is related to reduced reproductive skew. 2011 S. Karger AG, Basel.

  14. Lattice sites, charge states and spin–lattice relaxation of Fe ions in {sup 57}Mn{sup +} implanted GaN and AlN

    Energy Technology Data Exchange (ETDEWEB)

    Masenda, H., E-mail: hilary.masenda@wits.ac.za [School of Physics, University of the Witwatersrand, Johannesburg 2050 (South Africa); Naidoo, D. [School of Physics, University of the Witwatersrand, Johannesburg 2050 (South Africa); Bharuth-Ram, K. [Physics Department, Durban University of Technology, Durban 4000 (South Africa); iThemba LABS, PO Box 725, Somerset West 7129 (South Africa); Gunnlaugsson, H.P. [PH Department, ISOLDE/CERN, 1211 Geneva 23 (Switzerland); KU Leuven, Instituut voor Kern-en Stralingsfysica, 3001 Leuven (Belgium); Johnston, K. [PH Department, ISOLDE/CERN, 1211 Geneva 23 (Switzerland); Mantovan, R. [Laboratorio MDM, IMM-CNR, Via Olivetti 2, 20864 Agrate Brianza (MB) (Italy); Mølholt, T.E. [PH Department, ISOLDE/CERN, 1211 Geneva 23 (Switzerland); Ncube, M. [School of Physics, University of the Witwatersrand, Johannesburg 2050 (South Africa); Shayestehaminzadeh, S. [Materials Chemistry, RWTH Aachen University, Kopernikusstr. 10, 5274 Aachen (Germany); Gíslason, H.P. [Science Institute, University of Iceland, Dunhaga 3, 107 Reykjavík (Iceland); Langouche, G. [KU Leuven, Instituut voor Kern-en Stralingsfysica, 3001 Leuven (Belgium); Ólafsson, S. [Science Institute, University of Iceland, Dunhaga 3, 107 Reykjavík (Iceland); Weyer, G. [Department of Physics and Astronomy, Aarhus University, Ny Munkegade 120, 8000 Aarhus (Denmark)

    2016-03-01

    The lattice sites, valence states, resulting magnetic behaviour and spin–lattice relaxation of Fe ions in GaN and AlN were investigated by emission Mössbauer spectroscopy following the implantation of radioactive {sup 57}Mn{sup +} ions at ISOLDE/CERN. Angle dependent measurements performed at room temperature on the 14.4 keV γ-rays from the {sup 57}Fe Mössbauer state (populated from the {sup 57}Mn β{sup −} decay) reveal that the majority of the Fe ions are in the 2+ valence state nearly substituting the Ga and Al cations, and/or associated with vacancy type defects. Emission Mössbauer spectroscopy experiments conducted over a temperature range of 100–800 K show the presence of magnetically split sextets in the “wings” of the spectra for both materials. The temperature dependence of the sextets relates these spectral features to paramagnetic Fe{sup 3+} with rather slow spin–lattice relaxation rates which follow a T{sup 2} temperature dependence characteristic of a two-phonon Raman process. - Highlights: • The majority of the Fe ions are in the 2+ state, located on near substitutional sites associated with vacancy type defects. • A significant fraction of the Fe ions are in the paramagnetic Fe{sup 3+} state. • Spin–lattice relaxation of Fe{sup 3+} in both GaN and AlN follows a two-phonon Raman process.

  15. For Mole Problems, Call Avogadro: 602-1023

    Science.gov (United States)

    Uthe, R. E.

    2002-10-01

    General education students who have never encountered Avogadro’s number often have difficulty grasping its magnitude and the resulting implications for sizes and numbers of particles in common materials they see around them. I have surveyed the approaches used by several chemical educators. This article describes the techniques I find best help introductory students in General College at the University of Minnesota become familiar with Avogadro’s number and mole calculations. They involve estimating numbers of common objects and then calculating the length of time needed to count large numbers of them. For example, the immense amount of time required to count a mole of sand grains at one grain per second greatly exceeds the age of the universe. The calculations also reinforce procedures for manipulating exponents and applying problem-solving techniques.

  16. First-Principles Study of Defects in GaN, AlN and Their Alloys

    Science.gov (United States)

    2010-08-31

    defines the ionization energy. -12- Interstitial aluminum and aluminum vacancy pairs (Ali-VAl) in AlN In the previous program, we have...Following the general trends between phosphides, arsenides, and antimonides ,22 we expect the VBM of Zn3Sb2 to lie at least as high as that of Zn3P2

  17. Sandwich method to grow high quality AlN by MOCVD

    Science.gov (United States)

    Demir, I.; Li, H.; Robin, Y.; McClintock, R.; Elagoz, S.; Razeghi, M.

    2018-02-01

    We report pulsed atomic layer epitaxy growth of a very high crystalline quality, thick (~2 µm) and crack-free AlN material on c-plane sapphire substrates via a sandwich method using metal organic chemical vapor deposition. This sandwich method involves the introduction of a relatively low temperature (1050 °C) 1500 nm thick AlN layer between two 250 nm thick AlN layers which are grown at higher temperature (1170 °C). The surface morphology and crystalline quality remarkably improve using this sandwich method. A 2 µm thick AlN layer was realized with 33 arcsec and 136 arcsec full width at half maximum values for symmetric (0 0 0 2) and asymmetric ≤ft(1 0 \\bar{1} 5 \\right)~ reflections of ω-scan, respectively, and it has an atomic force microscopy root-mean-square surface roughness of ~0.71 nm for a 5  ×  5 µm2 surface area.

  18. Early and Late Retrieval of the ALN Removable Vena Cava Filter: Results from a Multicenter Study

    International Nuclear Information System (INIS)

    Pellerin, O.; Barral, F. G.; Lions, C.; Novelli, L.; Beregi, J. P.; Sapoval, M.

    2008-01-01

    Retrieval of removable inferior vena cava (IVC) filters in selected patients is widely practiced. The purpose of this multicenter study was to evaluate the feasibility and results of percutaneous removal of the ALN removable filter in a large patient cohort. Between November 2003 and June 2006, 123 consecutive patients were referred for percutaneous extraction of the ALN filter at three centers. The ALN filter is a removable filter that can be implanted through a femoral/jugular vein approach and extracted by the jugular vein approach. Filter removal was attempted after an implantation period of 93 ± 15 days (range, 6-722 days) through the right internal jugular vein approach using the dedicated extraction kit after control inferior vena cavography. Following filter removal, vena cavograms were obtained in all patients. Successful extraction was achieved in all but one case. Among these successful retrievals, additional manipulation using a femoral approach was needed when the apex of the filter was close to the IVC wall in two patients. No immediate IVC complications were observed according to the postimplantation cavography. Neither technical nor clinical differences between early and late filter retrieval were noticed. Our data confirm the safety of ALN filter retrieval up to 722 days after implantation. In infrequent cases, additional endovenous filter manipulation is needed to facilitate extraction.

  19. Effect of Cr implantation on structural and optical properties of AlN thin films

    Science.gov (United States)

    Shah, A.; Mahmood, Arshad

    2012-10-01

    Molecular beam epitaxy (MBE) grown AlN thin layer on sapphire substrates have been implanted with Cr+ ions for various dose from 1013 to 1015 cm-2. The analyses were carried out by an X-ray diffractometer (XRD), Raman spectroscopy, a spectrophotometer and spectroscopic ellipsometry (SE) for structural and optical analyses. E2(high) and A1(LO) Raman modes of AlN layer have been observed and analyzed. The behavior of Raman shift and the variation in intensity and in peak width of Raman modes as a function of ions flux are explained on the basis of chromium substituting aluminum atom and implantation-induced lattice damage. Both Raman and X-ray analyses reveal that the incorporation of chromium atoms increases in the host lattice with the increasing of Cr ions fluence. The band gap energy was determined by using transmission spectra. It was found that the band gap energy decreases as the ion dose increases. The band gap of the unimplanted AlN is 6.02 eV and it decreases down to 5.92 eV for the Cr+-implanted AlN with a ion dose of 1×1015 cm-2. Optical properties such as optical constants of the samples were examined by using a spectroscopic ellipsometer. It was observed that the refractive index (n) decreases with the increasing of ion dose.

  20. Cd doping of AlN via ion implantation studied with perturbed angular correlation

    CERN Document Server

    Kessler, Patrick; Miranda, Sérgio MC; Simon, R; Correia, João Guilherme; Johnston, Karl; Vianden, Reiner

    2012-01-01

    AlN with a wide bandgap of 6.2 eV is a promising candidate for ultraviolet light-emitting diodes and laser diodes. However, the production of the required p-type AlN is still challenging. As a possible dopant Cd was suggested among other Group II atoms (Be, Mg, and Zn). In this study the annealing condition of implanted Cd in AlN was investigated with the method of the perturbed angular correlation (PAC). Therefore radioactive $^{117}$Cd or $^{111m}$Cd ions were implanted into thin AlN films on sapphire substrate with an energy of 30 keV and fluences in the range of 10$^{11}$ ions/cm$^{2}$. After thorough annealing with a proximity cap of the same material most of the Cd-probes occupy substitutional lattice sites and almost all implantation damage can be annealed. This results in a distinct frequency in the PAC spectra which increases with temperature. In contrast to the formation of an indium nitrogen-vacancy complex observed with the probe $^{111}$In on substitutional Al-sites no defects are bound to substi...

  1. Structural properties, crystal quality and growth modes of MOCVD-grown AlN with TMAl pretreatment of sapphire substrate

    KAUST Repository

    Sun, Haiding

    2017-08-08

    The growth of high quality AlN epitaxial films relies on precise control of the initial growth stages. In this work, we examined the influence of the trimethylaluminum (TMAl) pretreatment of sapphire substrates on the structural properties, crystal quality and growth modes of heteroepitaxial AlN films on (0001) sapphire substrates. Without the pretreatment, the AlN films nucleated on the smooth surface but exhibited mixed crystallographic Al- (N-) polarity, resulting in rough AlN film surfaces. With increasing the pretreatment time from 1 to 5 s, the N-polarity started to be impeded. However, small islands were formed on sapphire surface due to the decompostion of TMAl. As a result, small voids became noticeable at the nucleation layer (NL) because the growth started as quasi three-dimensional (3D) but transformed to 2D mode as the film grew thicker and got coalesced, leading to smoother and Al-polar films. On the other hand, longer pretreatment time of 40 s formed large 3D islands on sapphire, and thus initiated a 3D-growth mode of the AlN film, generating Al-polar AlN nanocolumns with different facets, which resulted into rougher film surfaces. The epitaxial growth modes and their correlation with the AlN film crystal quality under different TMAl pretreatments are also discussed.

  2. In-situ growth mode control of AlN on SiC substrate by sublimation closed space technique

    Science.gov (United States)

    Dojima, Daichi; Ashida, Koji; Kaneko, Tadaaki

    2018-02-01

    For the growth of AlN single crystal with large diameter and low dislocation density on SiC substrate by physical vapor transport (PVT), a dislocation blocking buffer layer (DBBL) has been simply developed by optimizing the AlN growth parameters such as temperature gradient (ΔT), substrate temperature (Tsub), and N2 partial pressure (PN2) at the initial growth stage. Increase in ΔT resulted in the formation of an abrupt AlN/SiC interface due to the suppression of inhomogeneous thermal decomposition at the interface and the subsequent AlN unstable island growth. The well-defined AlN/SiC interface played an important role in controlling the two kinds of different AlN growth mode in-situ as functions of Tsub and PN2. One is a continuous step-flow growth mode, and the other is a discontinuous platelet-like growth. The discontinuous AlN layer, consisting of thin AlN platelets and air-gaps inserted between the two adjacent platelets, acted as the DBBL. By introducing the DBBL at the initial growth stage, followed by the step-flow growth, continuous AlN layer with dislocation density of 1.7 × 106 cm-2 was achieved at a total growth thickness of 60 μm, which is two orders of magnitude lower than the previously reported value.

  3. Synthesis of AlN whiskers using cobalt oxide catalyst and their alignments for the improvement of thermal conductivity

    Energy Technology Data Exchange (ETDEWEB)

    Dang, Thi My Linh [Nano-Convergence Materials Center, Korea Institute of Ceramic Engineering and Technology, Soho-ro 10, Jinju-si, Kyeoungsangnam-do, 660-031 (Korea, Republic of); Electronic Materials Lab., School of Advanced Materials Science and Engineering, SungKyunKwan Univ., Suwon-si, Gyeonggi-do, 440-746 (Korea, Republic of); Yoon, Dae-Ho, E-mail: dhyoon@skku.edu [Electronic Materials Lab., School of Advanced Materials Science and Engineering, SungKyunKwan Univ., Suwon-si, Gyeonggi-do, 440-746 (Korea, Republic of); Kim, Chang-Yeoul, E-mail: cykim15@kicet.re.kr [Nano-Convergence Materials Center, Korea Institute of Ceramic Engineering and Technology, Soho-ro 10, Jinju-si, Kyeoungsangnam-do, 660-031 (Korea, Republic of)

    2016-08-15

    We synthesized one dimensional (1-D) AlN whiskers by using the cobalt oxide catalyst-assisted carbothermal reduction method. The formation of AlN whiskers is investigated by the thermo-gravimetric and differential thermal analysis, Fourier-transformed infrared spectra, X-ray diffraction patterns, scanning electron microscopy and transmission electron microscopy observations. It was found that Co{sub 3}O{sub 4} droplets on the surfaces of Al{sub 2}O{sub 3} acted as a catalyst for the growth of AlN whiskers by vapor-liquid-solid (VLS) mechanism. In addition, AlN whiskers/PVA composites aligned in parallel with the heat flow direction showed an excellent thermal conductivity about three times higher than those of the perpendicularly aligned whisker composites. - Highlights: • AlN whiskers with high aspect ratio were synthesized from Al{sub 2}O{sub 3}. • Co{sub 3}O{sub 4} droplets on the surface of Al{sub 2}O{sub 3} acts as a catalyst for the whisker growth. • AlN whiskers are aligned within PVA in perpendicular and parallel with heat flow. • AlN whisker/PVA composite in perpendicular alignment shows a excellent heat conductivity.

  4. Investigation of Donor and Acceptor Ion Implantation in AlN

    Energy Technology Data Exchange (ETDEWEB)

    Osinsky, Andrei [Agnitron Technology Inc., Eden Prairie, MN (United States)

    2015-09-16

    AlGaN alloys with high Al composition and AlN based electronic devices are attractive for high voltage, high temperature applications, including microwave power sources, power switches and communication systems. AlN is of particular interest because of its wide bandgap of ~6.1eV which is ideal for power electronic device applications in extreme environments which requires high dose ion implantation. One of the major challenges that need to be addressed to achieve full utilization of AlN for opto and microelectronic applications is the development of a doping strategy for both donors and acceptors. Ion implantation is a particularly attractive approach since it allows for selected-area doping of semiconductors due to its high spatial and dose control and its high throughput capability. Active layers in the semiconductor are created by implanting a dopant species followed by very high temperature annealing to reduce defects and thereby activate the dopants. Recovery of implant damage in AlN requires excessively high temperature. In this SBIR program we began the investigation by simulation of ion beam implantation profiles for Mg, Ge and Si in AlN over wide dose and energy ranges. Si and Ge are implanted to achieve the n-type doping, Mg is investigated as a p-type doping. The simulation of implantation profiles were performed in collaboration between NRL and Agnitron using a commercial software known as Stopping and Range of Ions in Matter (SRIM). The simulation results were then used as the basis for ion implantation of AlN samples. The implanted samples were annealed by an innovative technique under different conditions and evaluated along the way. Raman spectroscopy and XRD were used to determine the crystal quality of the implanted samples, demonstrating the effectiveness of annealing in removing implant induced damage. Additionally, SIMS was used to verify that a nearly uniform doping profile was achieved near the sample surface. The electrical characteristics

  5. Local heteroepitaxy as an adhesion mechanism in aluminium coatings cold gas sprayed on AlN substrates

    International Nuclear Information System (INIS)

    Wüstefeld, Christina; Rafaja, David; Motylenko, Mykhaylo; Ullrich, Christiane; Drehmann, Rico; Grund, Thomas; Lampke, Thomas; Wielage, Bernhard

    2017-01-01

    Cold gas sprayed Al coatings deposited onto wurtzitic AlN substrates show excellent adhesion. As a possible adhesion mechanism, the local heteroepitaxy between Al and AlN was considered and verified experimentally in Al coatings, which were deposited using magnetron sputtering or cold gas spraying on single-crystalline and polycrystalline AlN substrates. Analysis of the local orientation relationships at the Al/AlN interfaces revealed that preferentially such lattice planes of Al align parallel with the upright lattice planes of AlN, which possess similar interplanar distances. The matching lattice planes in the Al coatings grew as continuations of the lattice planes in the AlN substrates. In all samples under study, the parallel alignment of the lattice planes {220} Al and {110} AlN was found. Additional orientation relationships between Al and AlN arose if parallel lattice planes with similar interplanar spacing could be found in both counterparts via rotation of the lattice planes {220} Al around their normal direction. Still, the oriented growth of Al on AlN is only possible if Al atoms in the deposited coatings are mobile enough to rearrange along the AlN surface. Whereas the mobility of Al atoms in a magnetron sputtering process is expected to be sufficiently high, the intrinsic mobility of Al atoms in the cold gas sprayed particles is anticipated to be low. However, the auxiliary microstructure analyses have shown that local recrystallization and partial melting are two phenomena, which can facilitate the rearrangement of Al atoms within the cold gas sprayed coating.

  6. C-axis orientated AlN films deposited using deep oscillation magnetron sputtering

    Energy Technology Data Exchange (ETDEWEB)

    Lin, Jianliang, E-mail: Jianliang.lin@swri.org [Southwest Research Institute, San Antonio, TX 78238 (United States); Chistyakov, Roman [Zpulser LLC, Mansfield, MA 02048 (United States)

    2017-02-28

    Highlights: • Highly <0001> orientated AlN films were deposited by DOMS technique. • Controlled ion flux bombardment improved the <0001> texture and crystalline quality. • Excessive ion bombardment showed a detrimental effect on the c-axis orientation growth. • Improved c-axis alignment accompanied with stress relaxation with increasing film thickness. - Abstract: Highly <0001> c-axis orientated aluminum nitride (AlN) films were deposited on silicon (100) substrates by reactive deep oscillation magnetron sputtering (DOMS). No epitaxial favored bond layer and substrate heating were applied for assisting texture growth. The effects of the peak target current density (varied from 0.39 to 0.8 Acm{sup −2}) and film thickness (varied from 0.25 to 3.3 μm) on the c-axis orientation, microstructure, residual stress and mechanical properties of the AlN films were investigated by means of X-ray diffraction rocking curve methodology, transmission electron microscopy, optical profilometry, and nanoindentation. All AlN films exhibited a <0001> preferred orientation and compressive residual stresses. At similar film thicknesses, an increase in the peak target current density to 0.53 Acm{sup −2} improved the <0001> orientation. Further increasing the peak target current density to above 0.53 Acm{sup −2} showed limited contribution to the texture development. The study also showed that an increase in the thickness of the AlN films deposited by DOMS improved the c-axis alignment accompanied with a reduction in the residual stress.

  7. Electrical Activation Studies of Silicon Implanted Aluminum Gallium Nitride with High Aluminum Mole Fraction

    Science.gov (United States)

    2007-12-01

    Marciniak, T. Zens, E. Moore, R. Hengehold Stiener. “ Electrica 283 Implanted AlxGa1-xN,” Journal of Electromagnetic Materials, 35(4): 647-653 36...Proceedings of the 2001:125-130 (2001). 286 68. Fellows, James A., Y. K. Yeo, Mee-Yi Ryu, and R. L. Hengehold. “ Electrica and Optical Activation

  8. Altered composition of liver proteasome assemblies contributes to enhanced proteasome activity in the exceptionally long-lived naked mole-rat.

    Science.gov (United States)

    Rodriguez, Karl A; Edrey, Yael H; Osmulski, Pawel; Gaczynska, Maria; Buffenstein, Rochelle

    2012-01-01

    The longest-lived rodent, the naked mole-rat (Bathyergidae; Heterocephalus glaber), maintains robust health for at least 75% of its 32 year lifespan, suggesting that the decline in genomic integrity or protein homeostasis routinely observed during aging, is either attenuated or delayed in this extraordinarily long-lived species. The ubiquitin proteasome system (UPS) plays an integral role in protein homeostasis by degrading oxidatively-damaged and misfolded proteins. In this study, we examined proteasome activity in naked mole-rats and mice in whole liver lysates as well as three subcellular fractions to probe the mechanisms behind the apparently enhanced effectiveness of UPS. We found that when compared with mouse samples, naked mole-rats had significantly higher chymotrypsin-like (ChT-L) activity and a two-fold increase in trypsin-like (T-L) in both whole lysates as well as cytosolic fractions. Native gel electrophoresis of the whole tissue lysates showed that the 20S proteasome was more active in the longer-lived species and that 26S proteasome was both more active and more populous. Western blot analyses revealed that both 19S subunits and immunoproteasome catalytic subunits are present in greater amounts in the naked mole-rat suggesting that the observed higher specific activity may be due to the greater proportion of immunoproteasomes in livers of healthy young adults. It thus appears that proteasomes in this species are primed for the efficient removal of stress-damaged proteins. Further characterization of the naked mole-rat proteasome and its regulation could lead to important insights on how the cells in these animals handle increased stress and protein damage to maintain a longer health in their tissues and ultimately a longer life.

  9. Altered composition of liver proteasome assemblies contributes to enhanced proteasome activity in the exceptionally long-lived naked mole-rat.

    Directory of Open Access Journals (Sweden)

    Karl A Rodriguez

    Full Text Available The longest-lived rodent, the naked mole-rat (Bathyergidae; Heterocephalus glaber, maintains robust health for at least 75% of its 32 year lifespan, suggesting that the decline in genomic integrity or protein homeostasis routinely observed during aging, is either attenuated or delayed in this extraordinarily long-lived species. The ubiquitin proteasome system (UPS plays an integral role in protein homeostasis by degrading oxidatively-damaged and misfolded proteins. In this study, we examined proteasome activity in naked mole-rats and mice in whole liver lysates as well as three subcellular fractions to probe the mechanisms behind the apparently enhanced effectiveness of UPS. We found that when compared with mouse samples, naked mole-rats had significantly higher chymotrypsin-like (ChT-L activity and a two-fold increase in trypsin-like (T-L in both whole lysates as well as cytosolic fractions. Native gel electrophoresis of the whole tissue lysates showed that the 20S proteasome was more active in the longer-lived species and that 26S proteasome was both more active and more populous. Western blot analyses revealed that both 19S subunits and immunoproteasome catalytic subunits are present in greater amounts in the naked mole-rat suggesting that the observed higher specific activity may be due to the greater proportion of immunoproteasomes in livers of healthy young adults. It thus appears that proteasomes in this species are primed for the efficient removal of stress-damaged proteins. Further characterization of the naked mole-rat proteasome and its regulation could lead to important insights on how the cells in these animals handle increased stress and protein damage to maintain a longer health in their tissues and ultimately a longer life.

  10. Improved crystalline quality of AlN epitaxial layer on sapphire by introducing TMGa pulse flow into the nucleation stage

    Science.gov (United States)

    Wu, Hualong; Wang, Hailong; Chen, Yingda; Zhang, Lingxia; Chen, Zimin; Wu, Zhisheng; Wang, Gang; Jiang, Hao

    2018-05-01

    The crystalline quality of AlN epitaxial layers on sapphire substrates was improved by introducing trimethylgallium (TMGa) pulse flow into the growth of AlN nucleation layers. It was found that the density of both screw- and edge-type threading dislocations could be significantly reduced by introducing the TMGa pulse flow. With increasing TMGa pulse flow times, the lateral correlation length (i.e. the grain size) increases and the strain in the AlN epilayers changes from tensile state to compressive state. Unstrained AlN with the least dislocations and a smooth surface was obtained by introducing 2-times TMGa pulse flow. The crystalline improvement is attributed to enhanced lateral growth and improved crystalline orientation by the TMGa pulse flow.

  11. Phase Composition and Microstructure of Hot-Pressing Sintered Ti2AlN Metal-Ceramic Bulk Material

    Directory of Open Access Journals (Sweden)

    LIANG Suying

    2017-06-01

    Full Text Available Ti2AlN metal-ceramic bulk material was fabricated by hot-pressing sintering (HPS using TiN, Ti and Al powder in a stoichiometric ratio of 1:1:1.03 after mechanical mixing. XRD, SEM and TEM were employed to investigate the phase composition and microstructures of the products. The results show that the high purity Ti2AlN can be obtained by HPS at 1300 ℃ for 2.5 h. The sintered Ti2AlN presented a hexagonal system layered structure with an anisotropy. Twins are found in the Ti2AlN. There were a few nano-scale TiN particles in the products.

  12. Growth and Comparison of Residual Stress of AlN Films on Silicon (100), (110) and (111) Substrates

    Science.gov (United States)

    Pandey, Akhilesh; Dutta, Shankar; Prakash, Ravi; Raman, R.; Kapoor, Ashok Kumar; Kaur, Davinder

    2018-02-01

    This paper reports on the comparison of residual stresses in AlN thin films sputter-deposited in identical conditions on Si (100) (110) and (111) substrates. The deposited films are of polycrystalline wurtzite structure with preferred orientation along the (002) direction. AlN film on the Si (111) substrate showed a vertical columnar structure, whereas films on Si (100) and (110) showed tilted columnar structures. Residual stress in the AlN films is estimated by x-ray diffraction (XRD), infra-red absorption method and wafer curvature technique. Films residual stress are found compressive and values are in the range of - 650 (± 50) MPa, - 730 (± 50) MPa and - 300 (± 50) MPa for the AlN films grown on Si (100), (110) and (111) substrates, respectively, with different techniques. The difference in residual stresses can be attributed to the microstructure of the films and mismatch between in plane atomic arrangements of the film and substrates.

  13. Hotzone design and optimization for 2-in. AlN PVT growth process through global heat transfer modeling and simulations

    Science.gov (United States)

    Wang, Z. H.; Deng, X. L.; Cao, K.; Wang, J.; Wu, L.

    2017-09-01

    A tungsten based reactor to grow 2-in. PVT AlN crystals by induction heating was designed. In order to investigate the effect of the hotzone structure layout on the temperature distribution in the growth chamber, a series of global quasi-steady numerical simulations with and without gas convection was performed using the FEMAG software. Simulation results show that the temperature gradient between the AlN powder sources and the deposition interface is influenced profoundly by the size of the induction heater and the crucible thickness. Also the tungsten heat shields have obvious effects on the global temperature distribution and heater power consumption during the growth process. However, the number of tungsten shield layers plays a trivial role on the temperature gradient between the ALN powder sources and the crucible top. Global heat transfer simulations show that the designed hotzone can provide an optimized and flexible environment for 2-in. AlN PVT growth.

  14. Improved performance of GaN based light emitting diodes with ex-situ sputtered AlN nucleation layers

    Directory of Open Access Journals (Sweden)

    Shuo-Wei Chen

    2016-04-01

    Full Text Available The crystal quality, electrical and optical properties of GaN based light emitting diodes (LEDs with ex-situ sputtered physical vapor deposition (PVD aluminum nitride (AlN nucleation layers were investigated. It was found that the crystal quality in terms of defect density and x-ray diffraction linewidth was greatly improved in comparison to LEDs with in-situ low temperature GaN nucleation layer. The light output power was 3.7% increased and the reverse bias voltage of leakage current was twice on LEDs with ex-situ PVD AlN nucleation layers. However, larger compressive strain was discovered in LEDs with ex-situ PVD AlN nucleation layers. The study shows the potential and constrain in applying ex-situ PVD AlN nucleation layers to fabricate high quality GaN crystals in various optoelectronics.

  15. Effects of Sputtering Parameters on AlN Film Growth on Flexible Hastelloy Tapes by Two-Step Deposition Technique.

    Science.gov (United States)

    Peng, Bin; Gong, Dongdong; Zhang, Wanli; Jiang, Jianying; Shu, Lin; Zhang, Yahui

    2016-08-10

    AlN thin films were deposited on flexible Hastelloy tapes and Si (100) substrate by middle-frequency magnetron sputtering. A layer of Y₂O₃ films was used as a buffer layer for the Hastelloy tapes. A two-step deposition technique was used to prepare the AlN films. The effects of deposition parameters such as sputtering power, N₂/Ar flow rate and sputtering pressure on the microstructure of the AlN thin films were systematically investigated. The results show that the dependency of the full width at half maximum (FWHM) of AlN/Y₂O₃/Hastelloy on the sputtering parameters is similar to that of AlN/Si (100). The FWHM of the AlN (002) peak of the prepared AlN films decreases with increasing sputtering power. The FWHM decreases with the increase of the N₂/Ar flow rate or sputtering pressure, and increases with the further increase of the N₂/Ar flow rate or sputtering pressure. The FWHM of the AlN/Y₂O₃/Hastelloy prepared under optimized parameters is only 3.7° and its root mean square (RMS) roughness is 5.46 nm. Based on the experimental results, the growth mechanism of AlN thin films prepared by the two-step deposition process was explored. This work would assist us in understanding the AlN film's growth mechanism of the two-step deposition process, preparing highly c-axis-oriented AlN films on flexible metal tapes and developing flexible surface acoustic wave (SAW) sensors from an application perspective.

  16. Bulk AlN crystal growth: self-seeding and seeding on 6H-SiC substrates

    Science.gov (United States)

    Edgar, J. H.; Liu, L.; Liu, B.; Zhuang, D.; Chaudhuri, J.; Kuball, M.; Rajasingam, S.

    2002-12-01

    The properties of bulk AlN crystals grown by sublimation recondensation and either randomly nucleated (i.e. self-seeded) or seeded on 6H-SiC substrates or compared. Self-seeding produces crystals of the highest perfection, lowest stress, and low Si and C impurity content, but the crystals grow in random crystallographic orientations. Crystals grown in boron nitride crucibles typically form thin platelets with the fastest growth occurring in the c-axis direction. Growth striations run the length of the crystals in the c-axis direction. Anisotropic etching in aqueous 45 wt% KOH solutions shows that the growth (0 0 0 1) planes exposed to the AlN source predominately have an aluminum polarity. AlN crystals seeded on 6H-SiC(0 0 0 1) have a single crystallographic orientation and the largest dimensions are perpendicular to the c-axis, determined by the size of the substrate. Cracking and voids in the AlN layer produced by differences in thermal expansion coefficients of AlN and SiC and decomposition of the SiC were ameliorated by depositing an AlN-SiC alloy layer on the SiC before growing the AlN layer. Raman spectroscopy measurements suggest the AlN and AlN-SiC alloy layer are both under tensile stress. The defect density in AlN crystals grown on composite AlN-SiC/6H-SiC substrates was 3.7×10 5 cm -2, as determined by synchrotron white beam X-ray topography.

  17. Memory and Electrical Properties of (100-Oriented AlN Thin Films Prepared by Radio Frequency Magnetron Sputtering

    Directory of Open Access Journals (Sweden)

    Maw-Shung Lee

    2014-01-01

    Full Text Available The (100-oriented aluminum nitride (AlN thin films were well deposited onto p-type Si substrate by radio frequency (RF magnetron sputtering method. The optimal deposition parameters were the RF power of 350 W, chamber pressure of 9 mTorr, and nitrogen concentration of 50%. Regarding the physical properties, the microstructure of as-deposited (002- and (100-oriented AlN thin films were obtained and compared by XRD patterns and TEM images. For electrical properties analysis, we found that the memory windows of (100-oriented AlN thin films are better than those of (002-oriented thin films. Besides, the interface and interaction between the silicon and (100-oriented AlN thin films was serious important problem. Finally, the current transport models of the as-deposited and annealed (100-oriented AlN thin films were also discussed. From the results, we suggested and investigated that large memory window of the annealed (100-oriented AlN thin films was induced by many dipoles and large electric field applied.

  18. Adult neurogenesis and its anatomical context in the hippocampus of three mole-rat species

    Directory of Open Access Journals (Sweden)

    Irmgard eAmrein

    2014-05-01

    Full Text Available African mole-rats (family Bathyergidae are small to medium sized, long-lived and strictly subterranean rodents that became valuable animal models as a result of their longevity and diversity in social organization. The formation and integration of new hippocampal neurons in adult mammals (adult hippocampal neurogenesis, AHN correlates negatively with age and positively with habitat complexity. Here we present quantitative data on AHN in wild-derived mole-rats of one year and older, and briefly describe its anatomical context including markers of neuronal function (calbindin and parvalbumin. Solitary Cape mole-rats (Georychus capensis, social highveld mole-rats (Cryptomys hottentotus pretoriae, and eusocial naked mole-rats (Heterocephalus glaber were assessed. Compared to other rodents, the hippocampal formation in mole-rats is small, but shows a distinct cytoarchitecture in the dentate gyrus and CA1. Distributions of the calcium-binding proteins differ from those seen in rodents; e.g., calbindin in CA3 of naked mole-rats distributes similar to the pattern seen in early primate development, and calbindin staining extends into the stratum lacunosum-moleculare of Cape mole-rats. Proliferating cells and young neurons are found in low numbers in the hippocampus of all three mole-rat species. Resident granule cell numbers are low as well. Proliferating cells expressed as a percentage of resident granule cells are in the range of other rodents, while the percentage of young neurons is lower than that observed in surface dwelling rodents. Between mole-rat species, we observed no difference in the percentage of proliferating cells. The percentages of young neurons are high in social highveld and naked mole-rats, and low in solitary Cape mole-rats. The findings support that proliferation is regulated independently of average life expectancy and habitat. Instead, neuronal differentiation reflects species-specific demands, which appear lower in subterranean

  19. Adult neurogenesis and its anatomical context in the hippocampus of three mole-rat species.

    Science.gov (United States)

    Amrein, Irmgard; Becker, Anton S; Engler, Stefanie; Huang, Shih-Hui; Müller, Julian; Slomianka, Lutz; Oosthuizen, Maria K

    2014-01-01

    African mole-rats (family Bathyergidae) are small to medium sized, long-lived, and strictly subterranean rodents that became valuable animal models as a result of their longevity and diversity in social organization. The formation and integration of new hippocampal neurons in adult mammals (adult hippocampal neurogenesis, AHN) correlates negatively with age and positively with habitat complexity. Here we present quantitative data on AHN in wild-derived mole-rats of 1 year and older, and briefly describe its anatomical context including markers of neuronal function (calbindin and parvalbumin). Solitary Cape mole-rats (Georychus capensis), social highveld mole-rats (Cryptomys hottentotus pretoriae), and eusocial naked mole-rats (Heterocephalus glaber) were assessed. Compared to other rodents, the hippocampal formation in mole-rats is small, but shows a distinct cytoarchitecture in the dentate gyrus and CA1. Distributions of the calcium-binding proteins differ from those seen in rodents; e.g., calbindin in CA3 of naked mole-rats distributes similar to the pattern seen in early primate development, and calbindin staining extends into the stratum lacunosum-moleculare of Cape mole-rats. Proliferating cells and young neurons are found in low numbers in the hippocampus of all three mole-rat species. Resident granule cell numbers are low as well. Proliferating cells expressed as a percentage of resident granule cells are in the range of other rodents, while the percentage of young neurons is lower than that observed in surface dwelling rodents. Between mole-rat species, we observed no difference in the percentage of proliferating cells. The percentages of young neurons are high in social highveld and naked mole-rats, and low in solitary Cape mole-rats. The findings support that proliferation is regulated independently of average life expectancy and habitat. Instead, neuronal differentiation reflects species-specific demands, which appear lower in subterranean rodents.

  20. High molecular weight hyaluronan mediates the cancer resistance of the naked mole-rat

    Science.gov (United States)

    Tian, Xiao; Azpurua, Jorge; Hine, Christopher; Vaidya, Amita; Myakishev-Rempel, Max; Ablaeva, Julia; Mao, Zhiyong; Nevo, Eviatar; Gorbunova, Vera; Seluanov, Andrei

    2013-01-01

    The naked mole-rat displays exceptional longevity, with a maximum lifespan exceeding 30 years1–3. This is the longest reported lifespan for a rodent species and is especially striking considering the small body mass of the naked mole-rat. In comparison, a similarly sized house mouse has a maximum lifespan of 4 years4,5. In addition to their longevity, naked mole-rats show an unusual resistance to cancer. Multi-year observations of large naked mole-rat colonies did not detect a single incidence of cancer2,6. Here we identify a mechanism responsible for the naked mole-rat’s cancer resistance. We found that naked mole-rat fibroblasts secrete extremely high molecular weight hyaluronan (HA), which is over five times larger than human or mouse HA. This high molecular weight HA accumulates abundantly in naked mole rat tissues due to the decreased activity of HA-degrading enzymes and a unique sequence of hyaluronan synthase 2 (HAS2). Furthermore, the naked mole-rat cells are more sensitive to HA signaling, as the naked mole rat cells have a higher affinity to HA than the mouse or human cells. Perturbation of the signaling pathways sufficient for malignant transformation of mouse fibroblasts fails to transform naked mole-rat cells. However, once high molecular weight HA is removed by either knocking down HAS2 or overexpressing the HA-degrading enzyme, Hyal2, naked mole-rat cells become susceptible to malignant transformation and readily form tumors in mice. We speculate that naked mole-rats have evolved a higher concentration of HA in the skin to provide skin elasticity needed for life in underground tunnels. This trait may have then been co-opted to provide cancer resistance and longevity to this species. PMID:23783513

  1. Properties of AlN thin films deposited by means of magnetron sputtering for ISFET applications

    Directory of Open Access Journals (Sweden)

    Firek Piotr

    2015-12-01

    Full Text Available This work presents the investigations of AlN thin films deposited on Si substrates by means of magnetron sputtering. Nine different sputtering processes were performed. Based on obtained results, the tenth process was prepared and performed (for future ISFET structures manufacturing. Round aluminum (Al electrodes were evaporated on the top of deposited layers. The MIS capacitor structures enabled a subsequent electrical characterization of the AlN films by means of current-voltage (I-V and capacitance-voltage (C-V measurements. Based on these results, the main parameters of investigated layers were obtained. Moreover, the paper describes the technology of fabrication and electrical characterization of ISFET transistors and possibility of their application as ion sensors.

  2. MOVPE-like HVPE of AlN using solid aluminum trichloride source

    Science.gov (United States)

    Eriguchi, Ken-ichi; Murakami, Hisashi; Panyukova, Uliana; Kumagai, Yoshinao; Ohira, Shigeo; Koukitu, Akinori

    2007-01-01

    A new MOVPE-like hydride vapor-phase epitaxy (HVPE) using AlCl 3 solid source is proposed for growing thick and high-quality AlN layers. For the new system, a high-purity AlCl 3 (5 N grade) powder was produced. AlN epitaxial layers were characterized by X-ray diffraction (XRD) and optical absorption measurement. Also, impurities such as oxygen and carbon in the epitaxial layer were analyzed comparing to the conventional HVPE system using Al metal and HCl gas. It is shown that the new HVPE system can be applied to mass production, because the Al-precursor can be transported to the reactor as vapor.

  3. Luminescence dynamics in AlGaN with AlN content of 20%

    KAUST Repository

    Soltani, Sonia

    2016-12-15

    Optical properties and carrier dynamics of an AlGaN layer with an AlN content of 20% have been studied using time-resolved photoluminescence (TR-PL). Despite the high density of defects due to the relatively high AlN content, an intense PL emission from the sample has been detected. Low-temperature PL spectra exhibit several features, accompanied by a strong emission-wavelength dependence of the PL decay time. A significant red-shift of more than 200 meV from the band edge is recorded for the PL emission from localized states. Temperature-dependent PL spectra of the sample are dominated by the emission from localized states and, furthermore, show a relatively slight decrease by almost an order of magnitude with increasing temperature from 45 to 300 K. Our observations indicate strong, spatial localization effects of carriers, resulting in an increase in the radiative recombination rate.

  4. Semipolar AlN and GaN on Si(100): HVPE technology and layer properties

    Science.gov (United States)

    Bessolov, V.; Kalmykov, A.; Konenkova, E.; Kukushkin, S.; Myasoedov, A.; Poletaev, N.; Rodin, S.

    2017-01-01

    Hydride vapor phase epitaxy (HVPE) growth of semipolar AlN and GaN layers on planar Si(100) substrates with SiC nanolayer is investigated. It is shown experimentally that the solid-phase epitaxial formation of a specially oriented SiC nucleation layer followed by epitaxy of AlN layer by HVPE at low rates enables growth of aluminum and gallium nitrides in the semipolar direction. For the best GaN(20-23) layers obtained, the full width at half maximum (FWHM) value for the x-ray diffraction rocking curve is 24 arcmin. The photoluminescence spectrum of the semipolar GaN measured at 4 K exhibits bands related to basal-plane and prismatic stacking faults (BSF and PSF).

  5. Fabrication and characterization of AlN metal-insulator-semiconductor grown Si substrate

    Science.gov (United States)

    Mahyuddin, A.; Azrina, A.; Mohd Yusoff, M. Z.; Hassan, Z.

    2017-11-01

    An experimental investigation was conducted to explore the effect of inserting a single AlGaN interlayer between AlN epilayer and GaN/AlN heterostructures on Si (111) grown by molecular beam epitaxy (MBE). It is confirmed from the scanning electron microscopy (SEM) that the AlGaN interlayer has a remarkable effect on reducing the tensile stress and dislocation density in AlN top layer. Capacitance-voltage (C-V) measurements were conducted to study the electrical properties of AlN/GaN heterostructures. While deriving the findings through the calculation it is suggested that the AlGaN interlayer can significantly reduce the value of effective oxide charge density and total effective number of charges per unit area which are 1.37 × 10-6C/cm2 and 8.55 × 1012cm-2, respectively.

  6. Electronic structure and chemical bonding anisotropy investigation of wurtzite AlN

    Science.gov (United States)

    Magnuson, M.; Mattesini, M.; Höglund, C.; Birch, J.; Hultman, L.

    2009-10-01

    The electronic structure and the anisotropy of the AlN π and σ chemical bonding of wurtzite AlN has been investigated by bulk-sensitive total fluorescence yield absorption and soft x-ray emission spectroscopies. The measured NK , AlL1 , and AlL2,3 x-ray emission and N1s x-ray absorption spectra are compared with calculated spectra using first-principles density-functional theory including dipole transition matrix elements. The main N2p-Al3p-Al 3d and N2p-Al3s hyridization regions are identified at -1.0 to -1.8eV and -5.0 to -5.5eV below the top of the valence band, respectively. In addition, N2s-Al3p and N2s-Al3s hybridization regions are found at the bottom of the valence band around -13.5 and -15eV , respectively. A strongly modified spectral shape of Al3s states in the AlL2,3 emission from AlN in comparison to Al metal is found, which is also reflected in the N2p-Al3p hybridization observed in the AlL1 emission. The differences between the electronic structure and chemical bonding of AlN and Al metal are discussed in relation to the position of the hybridization regions and the valence-band edge influencing the magnitude of the large band gap.

  7. INDEPENDENT EVALUATION OF THE GAM EX5ALN MINIATURE LINE-NARROWED KRF EXCIMER LASER

    Science.gov (United States)

    2017-06-01

    ABSTRACT The scope of this effort was to determine how the GAM Ex5ALN Line-Narrowed Ruggedized KrF Excimer Laser operates compared to the manufacturer’s... High -power, high -repetition rate excimer lasers are available from several US manufacturers. These systems are specifically designed for materials...to utilize high -power high -repetition rate laser systems for spectroscopy applications, where small bandwidth is important, has resulted in a need

  8. High molecular weight hyaluronan mediates the cancer resistance of the naked mole-rat

    OpenAIRE

    Tian, Xiao; Azpurua, Jorge; Hine, Christopher; Vaidya, Amita; Myakishev-Rempel, Max; Ablaeva, Julia; Mao, Zhiyong; Nevo, Eviatar; Gorbunova, Vera; Seluanov, Andrei

    2013-01-01

    The naked mole-rat displays exceptional longevity, with a maximum lifespan exceeding 30 years 1–3 . This is the longest reported lifespan for a rodent species and is especially striking considering the small body mass of the naked mole-rat. In comparison, a similarly sized house mouse has a maximum lifespan of 4 years 4,5 . In addition to their longevity, naked mole-rats show an unusual resistance to cancer. Multi-year observations of large naked mole-rat colonies did not detect a single inci...

  9. Sublimation growth of nonpolar AlN single crystals and defect characterization

    Energy Technology Data Exchange (ETDEWEB)

    Satoh, Issei; Arakawa, Satoshi; Tanizaki, Keisuke; Miyanaga, Michimasa; Yamamoto, Yoshiyuki [Sumitomo Electric Industries, Ltd., 1-1-1 Koyakita, Itami, Hyogo 664-0016 (Japan)

    2010-07-15

    Sublimation growth of nonpolar AlN single crystals was investigated. The crystals were prepared in two methods: By slicing along the m -plane from c -plane-grown thick crystals, and by heteroepitaxial growth on m -plane SiC substrates. Defects of the crystals were observed by high-resolution transmission electron microscope. Dislocation density in AlN/SiC (0001) decreased significantly at about 1.5 {mu}m above the interface, while stacking faults initiated from the interface toward the growth surface in AlN/SiC (1-100). With increasing crystal thickness, the dislocation density decreases up to 5 x 10{sup 4}/cm{sup 2} at the thickness of 10 mm. In the AlN single crystal grown on SiC (0001), it is noteworthy that the dislocations are localized around the AlN/SiC interface and that far fewer dislocations occur near the growth surface. High-crystallinity AlN thick single crystals could be grown on SiC (0001) substrates. (copyright 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  10. Influence of TMAl preflow on AlN epitaxy on sapphire

    KAUST Repository

    Sun, Haiding

    2017-05-12

    The trimethylaluminum (TMAl) preflow process has been widely applied on sapphire substrates prior to growing Al-polar AlN films by metalorganic chemical vapor deposition. However, it has been unclear how the TMAl preflow process really works. In this letter, we reported on carbon\\'s significance in the polarity and growth mode of AlN films due to the TMAl preflow. Without the preflow, no trace of carbon was found at the AlN/sapphire interface and the films possessed mixed Al- and N-polarity. With the 5 s preflow, carbon started to precipitate due to the decomposition of TMAl, forming scattered carbon-rich clusters which were graphitic carbon. It was discovered that the carbon attracted surrounding oxygen impurity atoms and consequently suppressed the formation of AlxOyNz and thus N-polarity. With the 40 s preflow, the significant presence of carbon clusters at the AlN/sapphire interface was observed. While still attracting oxygen and preventing the N-polarity, the carbon clusters served as randomly distributed masks to further induce a 3D growth mode for the AlN growth. The corresponding epitaxial growth mode change is discussed.

  11. Optical Properties Dependence with Gas Pressure in AlN Films Deposited by Pulsed Laser Ablation

    International Nuclear Information System (INIS)

    Perez, J A; Riascos, H; Caicedo, J C; Cabrera, G; Yate, L

    2011-01-01

    AlN films were deposited by pulsed laser deposition technique (PLD) using an Nd: YAG laser (λ = 1064 nm). The films were deposited in a nitrogen atmosphere as working gas; the target was an aluminum high purity (99.99%). The films were deposited with a laser fluence of 7 J/cm2 for 10 minutes on silicon (100) substrates. The substrate temperature was 300 deg. C and the working pressure was varied from 3 mtorr to 11 mtorr. The thickness measured by profilometer was 150 nm for all films. The crystallinity was observed via XRD pattern, the morphology and composition of the films were studied using scanning electron microscopy (SEM) and Energy Dispersive X-ray analysis (EDX), respectively. The optical reflectance spectra and color coordinates of the films were obtained by optical spectral reflectometry technique in the range of 400 cm-1- 900 cm-1 by an Ocean Optics 2000 spectrophotometer. In this work, a clear dependence of the reflectance, dominant wavelength and color purity was found in terms of the applied pressure to the AlN films. A reduction in reflectance of about 55% when the pressure was increased from 3 mtorr to 11 mtorr was observed. This paper deals with the formation of AlN thin films as promising materials for the integration of SAW devices on Si substrates due to their good piezoelectric properties and the possibility of deposition at low temperature compatible with the manufacturing of Si integrated circuits.

  12. Optical identification of silicon as a shallow donor in MOVPE grown homoepitaxial AlN

    Energy Technology Data Exchange (ETDEWEB)

    Neuschl, Benjamin; Thonke, Klaus [Institut fuer Quantenmaterie/Gruppe Halbleiterphysik, Universitaet Ulm, Ulm (Germany); Feneberg, Martin [Institut fuer Experimentelle Physik, Otto-von-Guericke-Universitaet-Magdeburg, Magdeburg (Germany); Mita, Seiji; Xie, Jinqiao; Dalmau, Rafael [HexaTech, Inc., 991 Aviation Pkwy., Suite 800, Morrisville, North Carolina 27560 (United States); Collazo, Ramon; Sitar, Zlatko [Department of Materials Science and Engineering, North Carolina State University, Raleigh, North Carolina (United States)

    2012-03-15

    Aluminum nitride (AlN) layers doped intentionally with different concentrations of silicon atoms acting as shallow donors were grown by MOVPE on bulk c-plane AlN to minimize dislocations in the doped layers; typical values for the dislocation density in the bulk AlN substrates are less than 10{sup 4} cm{sup -2}. The actual silicon concentration was confirmed by secondary ion mass spectroscopy (SIMS) analysis and ranging from 10{sup 17} to 10{sup 19} cm{sup -3}. In highly resolved low temperature photoluminescence (PL) investigations, we found dominating bandgap-related sharp emission lines with linewidth lower than 500 {mu}eV for undoped samples. We tentatively assign silicon as the shallow donor causing the bound exciton line with 28.5 meV exciton localization energy, for which we found an intensity ratio relative to the free exciton line being linearly dependent on the silicon concentration. For increasing Si content, the respective emission band also broadened asymmetrically and shifted to lower energies as expected from the analogy with other semiconductor systems. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  13. Resonator structures on AlN ceramics surface treated by laser radiation

    Science.gov (United States)

    Koziol, Pawel E.; Antonczak, Arkadiusz J.; Stepak, Bogusz; Gorski, Przemyslaw A.; Walczakowski, Michal; Palka, Norbert; Abramski, Krzysztof M.

    2014-03-01

    In this paper a method for producing resonant structures using laser micromachining is presented. In the spot of laser beam impact on AlN ceramics surface a conductive aluminum layer is formed. Compilation of process parameters allows for the fabrication of structures with resistance at Rs ~ 0.01Ω/Rs. It has been also found out that the maximum value of resistance for which spiral resonator structures manifest their unique properties is at the level of Rs = 1.43 Ω. Furthermore, the occurrence of mutual capacity which value is dependent on the arrangement of individual SR structures with respect to each other was observed and examined. Based on satisfactory results for SR structures, it has been attempted to produce a resonant structures dedicated to the THz range based on the process of direct metallization of AlN ceramics surface. As a result, the Split Ring Resonator structure whose properties were verified by using the THz -TDS method was manufactured. In case of the field E perpendicular to SRR structure and one resonance area for 0.50 THz with field E parallel to the structure, two characteristic resonant dips for 0.22 THz and 0.46 THz were obtained. The studies confirmed that the method of direct metallization of AlN ceramics allows to produce resonant structures in the THz range.

  14. Deep SiO2 etching with Al and AlN masks for MEMS devices

    Science.gov (United States)

    Bliznetsov, Vladimir; Mao Lin, Hua; Zhang, Yue Jia; Johnson, David

    2015-08-01

    Silicon oxide-based materials such as quartz and silica are widely used in microelectromechanical systems (MEMS). One way to enhance the capability of their deep plasma etching is to increase selectivity by the use of hard masks. Although this approach was studied previously, information on the use of hard masks for the etching of silicon-oxide based materials on 200 mm substrates is scarce. We present the results of etching process development for amorphous silicon oxide using Al and AlN masks with a view of the application of the results for the etching of silica and quartz. Three gas chemistries (C4F8/O2, CF4 and SF6) and their mixtures were compared in an industrial reactive ion etch (RIE) chamber with two plasma sources. It was established that pure SF6 is the best etchant and AlN is a better mask than Al for providing higher selectivity and a sidewall angle close to vertical. A range of etching parameters for micromasking-free etching was established and etched structures of up to a 4 : 1 aspect ratio were created in 21 μm-thick oxide using the process with an etch rate of 0.32-0.36 μm min-1 and a selectivity to AlN mask of (38-49) : 1.

  15. Optical Properties Dependence with Gas Pressure in AlN Films Deposited by Pulsed Laser Ablation

    Energy Technology Data Exchange (ETDEWEB)

    Perez, J A; Riascos, H [Departamento de Fisica, Universidad Tecnologica de Pereira, Grupo plasma Laser y Aplicaciones A.A 097 (Colombia); Caicedo, J C [Grupo pelIculas delgadas, Universidad del Valle, Cali (Colombia); Cabrera, G; Yate, L, E-mail: jcaicedoangulo@gmail.com [Department de Fisica Aplicada i Optica, Universitat de Barcelona, Catalunya (Spain)

    2011-01-01

    AlN films were deposited by pulsed laser deposition technique (PLD) using an Nd: YAG laser ({lambda} = 1064 nm). The films were deposited in a nitrogen atmosphere as working gas; the target was an aluminum high purity (99.99%). The films were deposited with a laser fluence of 7 J/cm2 for 10 minutes on silicon (100) substrates. The substrate temperature was 300 deg. C and the working pressure was varied from 3 mtorr to 11 mtorr. The thickness measured by profilometer was 150 nm for all films. The crystallinity was observed via XRD pattern, the morphology and composition of the films were studied using scanning electron microscopy (SEM) and Energy Dispersive X-ray analysis (EDX), respectively. The optical reflectance spectra and color coordinates of the films were obtained by optical spectral reflectometry technique in the range of 400 cm-1- 900 cm-1 by an Ocean Optics 2000 spectrophotometer. In this work, a clear dependence of the reflectance, dominant wavelength and color purity was found in terms of the applied pressure to the AlN films. A reduction in reflectance of about 55% when the pressure was increased from 3 mtorr to 11 mtorr was observed. This paper deals with the formation of AlN thin films as promising materials for the integration of SAW devices on Si substrates due to their good piezoelectric properties and the possibility of deposition at low temperature compatible with the manufacturing of Si integrated circuits.

  16. [Complete hydatiforme mole in Morocco: epidemiological and clinical study].

    Science.gov (United States)

    Boufettal, H; Coullin, P; Mahdaoui, S; Noun, M; Hermas, S; Samouh, N

    2011-09-01

    Complete hydatidiform moles (CHM) are a real public health problem, especially in the "southern countries" and Asia, because of their impact on the female reproduction and the risk to progression to either invasive mole or choriocarcinoma. We collected the cases of CHM referred to our department over a period of ten years (2000 to 2009). We will present our results, emphasize the modalities of diagnosis, treatment and evolution, with a review of literature. During this study, we identified 254 cases of CHM, and recorded 57,987 births and 1627 abortions. Their incidence was 0.43% of pregnancies. The mean age of our patients is 25 years old (16 to 55). Relative risk observed was much increased among women under 20 years old (×6.8) and those over 40 years old (×15). Both of nulliparous and primiparous patients represented 52.3% of the cohort. Eighty-five percent of patients belonged to an agricultural environment associated with a low socio-economic status. Uterine bleeding was the most common symptom accounting for 93.7%. Toxic syndrome was present in 18.5% of patients. Physical examination showed a highly increased uterine size in 85% of cases associated with lateral uterine mass in 25% of cases. The diagnosis was suspected using ultrasonography in all cases associated with an elevated level of plasmatic β-human chorionic gonadotrophin (βhCG). All cases were confirmed histologically. Treatment used was endo-uterine aspiration in all cases. Recurrence of CHM was documented in 25 patients or 9.4%. Neoplasic progression was observed for 6.3% of cases. All of them have evolved into remission with chemotherapy. CHM continue to be a public health problem in Morocco, their incidence is among the highest ones. In fact, this studied population corresponds to the lowest socio-economic status and generally described as population at risk. It is subject to drastic weather's conditions causing loss of fresh products. Extreme ages and degree of parity are also risk factors

  17. Optical, Structural and Paramagnetic Properties of Eu-Doped Ternary Sulfides ALnS2 (A = Na, K, Rb; Ln = La, Gd, Lu, Y

    Directory of Open Access Journals (Sweden)

    Vítězslav Jarý

    2015-10-01

    Full Text Available Eu-doped ternary sulfides of general formula ALnS2 (A = Na, K, Rb; Ln = La, Gd, Lu, Y are presented as a novel interesting material family which may find usage as X-ray phosphors or solid state white light emitting diode (LED lighting. Samples were synthesized in the form of transparent crystalline hexagonal platelets by chemical reaction under the flow of hydrogen sulfide. Their physical properties were investigated by means of X-ray diffraction, time-resolved photoluminescence spectroscopy, electron paramagnetic resonance, and X-ray excited fluorescence. Corresponding characteristics, including absorption, radioluminescence, photoluminescence excitation and emission spectra, and decay kinetics curves, were measured and evaluated in a broad temperature range (8–800 K. Calculations including quantum local crystal field potential and spin-Hamiltonian for a paramagnetic particle in D3d local symmetry and phenomenological model dealing with excited state dynamics were performed to explain the experimentally observed features. Based on the results, an energy diagram of lanthanide energy levels in KLuS2 is proposed. Color model xy-coordinates are used to compare effects of dopants on the resulting spectrum. The application potential of the mentioned compounds in the field of white LED solid state lighting or X-ray phosphors is thoroughly discussed.

  18. Pendeo-epitaxy of stress-free AlN layer on a profiled SiC/Si substrate

    Energy Technology Data Exchange (ETDEWEB)

    Bessolov, V.N. [Ioffe Physical Technical Institute, Russian Academy of Sciences, Politekhnicheskaya 26, St. Petersburg, 194021 (Russian Federation); Institute of Problems of Mechanical Engineering, Russian Academy of Sciences, V.O., Bolshoj pr., 61, St. Petersburg, 199178 (Russian Federation); Karpov, D.V. [St. Petersburg Academic University - Nanotechnology Research and Education Centre of the Russian Academy of Sciences (Academic University), Khlopina 8/3, St Petersburg, 194021 (Russian Federation); University of Eastern Finland, P.O. Box 111, Joensuu, 80101 (Finland); Konenkova, E.V. [Ioffe Physical Technical Institute, Russian Academy of Sciences, Politekhnicheskaya 26, St. Petersburg, 194021 (Russian Federation); Institute of Problems of Mechanical Engineering, Russian Academy of Sciences, V.O., Bolshoj pr., 61, St. Petersburg, 199178 (Russian Federation); Lipovskii, A.A. [St. Petersburg Academic University - Nanotechnology Research and Education Centre of the Russian Academy of Sciences (Academic University), Khlopina 8/3, St Petersburg, 194021 (Russian Federation); Peter the Great St. Petersburg Polytechnic University, Politekhnicheskaya 29, St. Petersburg, 195251 (Russian Federation); Osipov, A.V. [Institute of Problems of Mechanical Engineering, Russian Academy of Sciences, V.O., Bolshoj pr., 61, St. Petersburg, 199178 (Russian Federation); St. Petersburg National Research University of Information Technologies, Mechanics and Optics, Kronverkskii pr. 49, St. Petersburg, 197101 (Russian Federation); Redkov, A.V. [Institute of Problems of Mechanical Engineering, Russian Academy of Sciences, V.O., Bolshoj pr., 61, St. Petersburg, 199178 (Russian Federation); St. Petersburg Academic University - Nanotechnology Research and Education Centre of the Russian Academy of Sciences (Academic University), Khlopina 8/3, St Petersburg, 194021 (Russian Federation); Peter the Great St. Petersburg Polytechnic University, Politekhnicheskaya 29, St. Petersburg, 195251 (Russian Federation); and others

    2016-05-01

    A new approach to the pendeo-epitaxy of elastically-unstrained AlN films is developed. The AlN films are grown using chloride-hydride vapor phase epitaxy (HVPE) on a silicon substrate with specially synthesized and shaped buffer layer of nano-SiC (NSiC). This NSiC epitaxial layer is grown using a new technique based on the substitution of a part of silicon atoms by carbon ones in a 100–110 nm thick subsurface layer of the silicon substrate. The 2D array of ~ 200 nm in diameter wells with the depth of ~ 70 nm that is less than the NSiC layer thickness is formed on the NSiC surface using electron beam lithography followed by reactive ion etching, the period of the array is of 400 nm. In a single HVPE process we grew ~ 20 μm thick AlN film both on the shaped and smooth regions of the prepared substrate. The AlN films are examined with reflection high energy electron diffraction, X-ray diffractometry, Raman spectroscopy and scanning electron microscopy. We use the results of these measurements to compare residual elastic stresses in the AlN film grown on the shaped and smooth regions of the substrate. The film on the shaped part of the substrate is elastically-unstrained contrary to the smooth part where elastic stresses result in the formation of a textured AlN layer. The model of the AlN growth on shaped SiC/Si substrates prepared using the atomic substitution technique is proposed. - Highlights: • A new method for chloride-hydride vapor phase pendeo-epitaxy of AlN is proposed • Unstrained AlN layer is grown on a Si substrate with a nanoprofiled SiC buffer • SiC made by substitution of atoms is well suited for the growth of AlN • Dissolution of pores in silicon beneath the nano-SiC is revealed.

  19. A phylogenetic estimate for golden moles (Mammalia, Afrotheria, Chrysochloridae

    Directory of Open Access Journals (Sweden)

    Bloomer Paulette

    2010-03-01

    Full Text Available Abstract Background Golden moles (Chrysochloridae are small, subterranean, afrotherian mammals from South Africa and neighboring regions. Of the 21 species now recognized, some (e.g., Chrysochloris asiatica, Amblysomus hottentotus are relatively common, whereas others (e.g., species of Chrysospalax, Cryptochloris, Neamblysomus are rare and endangered. Here, we use a combined analysis of partial sequences of the nuclear GHR gene and morphological characters to derive a phylogeny of species in the family Chrysochloridae. Results Although not all nodes of the combined analysis have high support values, the overall pattern of relationships obtained from different methods of phylogeny reconstruction allow us to make several recommendations regarding the current taxonomy of golden moles. We elevate Huetia to generic status to include the species leucorhinus and confirm the use of the Linnean binomial Carpitalpa arendsi, which belongs within Amblysominae along with Amblysomus and Neamblysomus. A second group, Chrysochlorinae, includes Chrysochloris, Cryptochloris, Huetia, Eremitalpa, Chrysospalax, and Calcochloris. Bayesian methods make chrysochlorines paraphyletic by placing the root within them, coinciding with root positions favored by a majority of randomly-generated outgroup taxa. Maximum Parsimony (MP places the root either between chrysochlorines and amblysomines (with Chlorotalpa as sister taxon to amblysomines, or at Chlorotalpa, with the former two groups reconstructed as monophyletic in all optimal MP trees. Conclusions The inclusion of additional genetic loci for this clade is important to confirm our taxonomic results and resolve the chrysochlorid root. Nevertheless, our optimal topologies support a division of chrysochlorids into amblysomines and chrysochlorines, with Chlorotalpa intermediate between the two. Furthermore, evolution of the chrysochlorid malleus exhibits homoplasy. The elongate malleus has evolved just once in the

  20. A phylogenetic estimate for golden moles (Mammalia, Afrotheria, Chrysochloridae).

    Science.gov (United States)

    Asher, Robert J; Maree, Sarita; Bronner, Gary; Bennett, Nigel C; Bloomer, Paulette; Czechowski, Paul; Meyer, Matthias; Hofreiter, Michael

    2010-03-09

    Golden moles (Chrysochloridae) are small, subterranean, afrotherian mammals from South Africa and neighboring regions. Of the 21 species now recognized, some (e.g., Chrysochloris asiatica, Amblysomus hottentotus) are relatively common, whereas others (e.g., species of Chrysospalax, Cryptochloris, Neamblysomus) are rare and endangered. Here, we use a combined analysis of partial sequences of the nuclear GHR gene and morphological characters to derive a phylogeny of species in the family Chrysochloridae. Although not all nodes of the combined analysis have high support values, the overall pattern of relationships obtained from different methods of phylogeny reconstruction allow us to make several recommendations regarding the current taxonomy of golden moles. We elevate Huetia to generic status to include the species leucorhinus and confirm the use of the Linnean binomial Carpitalpa arendsi, which belongs within Amblysominae along with Amblysomus and Neamblysomus. A second group, Chrysochlorinae, includes Chrysochloris, Cryptochloris, Huetia, Eremitalpa, Chrysospalax, and Calcochloris. Bayesian methods make chrysochlorines paraphyletic by placing the root within them, coinciding with root positions favored by a majority of randomly-generated outgroup taxa. Maximum Parsimony (MP) places the root either between chrysochlorines and amblysomines (with Chlorotalpa as sister taxon to amblysomines), or at Chlorotalpa, with the former two groups reconstructed as monophyletic in all optimal MP trees. The inclusion of additional genetic loci for this clade is important to confirm our taxonomic results and resolve the chrysochlorid root. Nevertheless, our optimal topologies support a division of chrysochlorids into amblysomines and chrysochlorines, with Chlorotalpa intermediate between the two. Furthermore, evolution of the chrysochlorid malleus exhibits homoplasy. The elongate malleus has evolved just once in the Cryptochloris-Chrysochloris group; other changes in shape have

  1. High-molecular-mass hyaluronan mediates the cancer resistance of the naked mole rat.

    Science.gov (United States)

    Tian, Xiao; Azpurua, Jorge; Hine, Christopher; Vaidya, Amita; Myakishev-Rempel, Max; Ablaeva, Julia; Mao, Zhiyong; Nevo, Eviatar; Gorbunova, Vera; Seluanov, Andrei

    2013-07-18

    The naked mole rat (Heterocephalus glaber) displays exceptional longevity, with a maximum lifespan exceeding 30 years. This is the longest reported lifespan for a rodent species and is especially striking considering the small body mass of the naked mole rat. In comparison, a similarly sized house mouse has a maximum lifespan of 4 years. In addition to their longevity, naked mole rats show an unusual resistance to cancer. Multi-year observations of large naked mole-rat colonies did not detect a single incidence of cancer. Here we identify a mechanism responsible for the naked mole rat's cancer resistance. We found that naked mole-rat fibroblasts secrete extremely high-molecular-mass hyaluronan (HA), which is over five times larger than human or mouse HA. This high-molecular-mass HA accumulates abundantly in naked mole-rat tissues owing to the decreased activity of HA-degrading enzymes and a unique sequence of hyaluronan synthase 2 (HAS2). Furthermore, the naked mole-rat cells are more sensitive to HA signalling, as they have a higher affinity to HA compared with mouse or human cells. Perturbation of the signalling pathways sufficient for malignant transformation of mouse fibroblasts fails to transform naked mole-rat cells. However, once high-molecular-mass HA is removed by either knocking down HAS2 or overexpressing the HA-degrading enzyme, HYAL2, naked mole-rat cells become susceptible to malignant transformation and readily form tumours in mice. We speculate that naked mole rats have evolved a higher concentration of HA in the skin to provide skin elasticity needed for life in underground tunnels. This trait may have then been co-opted to provide cancer resistance and longevity to this species.

  2. FRACTIONAL BANKING

    OpenAIRE

    Maria Klimikova

    2010-01-01

    Understanding the reasons of the present financial problems lies In understanding the substance of fractional reserve banking. The substance of fractional banking is in lending more money than the bankers have. Banking of partial reserves is an alternative form which links deposit banking and credit banking. Fractional banking is causing many unfavorable economic impacts in the worldwide system, specifically an inflation.

  3. Twin Gestation Consisting of Hydatidiform Mole and a Live Fetus: A ...

    African Journals Online (AJOL)

    Ultrasonography revealed hydatidiform mole and a viable fetus. She had suction curettage at 16weeks gestational age because of heavy vaginal bleeding. Histology confirmed benign hydatidiform mole. Urinary HCG level declined progressively and was negative by 4 weeks post-evacuation. Eight months after, she was 20 ...

  4. How mole ratio of UF resin affects formaldehyde emission and other properties : a literature critique

    Science.gov (United States)

    George E. Myers

    1984-01-01

    A critical review was made of the literature concerned with how the formaldehyde to urea mole ratio (F/U) affects formaldehyde emission from particleboard and plywood bonded with urea-formaldehyde (UF) adhesives, and how this ratio affects certain other adhesive and board properties. It is difficult to quantify the dependence of various properties on mole ratio or...

  5. Trading new neurons for status: Adult hippocampal neurogenesis in eusocial Damaraland mole-rats.

    Science.gov (United States)

    Oosthuizen, M K; Amrein, I

    2016-06-02

    Diversity in social structures, from solitary to eusocial, is a prominent feature of subterranean African mole-rat species. Damaraland mole-rats are eusocial, they live in colonies that are characterized by a reproductive division of labor and a subdivision into castes based on physiology and behavior. Damaraland mole-rats are exceptionally long lived and reproductive animals show delayed aging compared to non-reproductive animals. In the present study, we described the hippocampal architecture and the rate of hippocampal neurogenesis of wild-derived, adult Damaraland mole-rats in relation to sex, relative age and social status or caste. Overall, Damaraland mole-rats were found to have a small hippocampus and low rates of neurogenesis. We found no correlation between neurogenesis and sex or relative age. Social status or caste was the most prominent modulator of neurogenesis. An inverse relationship between neurogenesis and social status was apparent, with queens displaying the lowest neurogenesis while the worker mole-rats had the most. As there is no natural progression from one caste to another, social status within a colony was relatively stable and is reflected in the level of neurogenesis. Our results correspond to those found in the naked mole-rat, and may reflect an evolutionary and environmentally conserved trait within social mole-rat species. Copyright © 2016 IBRO. Published by Elsevier Ltd. All rights reserved.

  6. The risk of persistent trophoblastic disease after hydatidiform mole classified by morphology and ploidy

    DEFF Research Database (Denmark)

    Niemann, Isa; Hansen, Estrid S; Sunde, Lone

    2007-01-01

    influence the development of morphologic features in hydatidiform moles. We recommend that gestations suspected of hydatidiform mole are subjected to histopathologic examination. If hydatidiform change and trophoblastic hyperplasia are identified, the ploidy should be used to identify patients with a high...

  7. Clinical management and diagnostic possibilities in hydatidiform mole with coexistent fetus

    DEFF Research Database (Denmark)

    Vejerslev, L O

    1991-01-01

    The goal of the current review is to present the figures essential for counseling, when hydatidiform mole and normal fetus occur together. Previous reviews of prognosis and risks when mole and fetus are observed together did not adjust for differences in genetic constitution and thus varying risk...

  8. The Naked Mole Rat Genome Resource: facilitating analyses of cancer and longevity-related adaptations.

    Science.gov (United States)

    Keane, Michael; Craig, Thomas; Alföldi, Jessica; Berlin, Aaron M; Johnson, Jeremy; Seluanov, Andrei; Gorbunova, Vera; Di Palma, Federica; Lindblad-Toh, Kerstin; Church, George M; de Magalhães, João Pedro

    2014-12-15

    The naked mole rat (Heterocephalus glaber) is an exceptionally long-lived and cancer-resistant rodent native to East Africa. Although its genome was previously sequenced, here we report a new assembly sequenced by us with substantially higher N50 values for scaffolds and contigs. We analyzed the annotation of this new improved assembly and identified candidate genomic adaptations which may have contributed to the evolution of the naked mole rat's extraordinary traits, including in regions of p53, and the hyaluronan receptors CD44 and HMMR (RHAMM). Furthermore, we developed a freely available web portal, the Naked Mole Rat Genome Resource (http://www.naked-mole-rat.org), featuring the data and results of our analysis, to assist researchers interested in the genome and genes of the naked mole rat, and also to facilitate further studies on this fascinating species. © The Author 2014. Published by Oxford University Press.

  9. Genome sequencing reveals insights into physiology and longevity of the naked mole rat

    DEFF Research Database (Denmark)

    Kim, Eun Bae; Fang, Xiaodong; Fushan, Alexey A

    2011-01-01

    The naked mole rat (Heterocephalus glaber) is a strictly subterranean, extraordinarily long-lived eusocial mammal. Although it is the size of a mouse, its maximum lifespan exceeds 30 years, making this animal the longest-living rodent. Naked mole rats show negligible senescence, no age......-related increase in mortality, and high fecundity until death. In addition to delayed ageing, they are resistant to both spontaneous cancer and experimentally induced tumorigenesis. Naked mole rats pose a challenge to the theories that link ageing, cancer and redox homeostasis. Although characterized...... by significant oxidative stress, the naked mole rat proteome does not show age-related susceptibility to oxidative damage or increased ubiquitination. Naked mole rats naturally reside in large colonies with a single breeding female, the 'queen', who suppresses the sexual maturity of her subordinates. They also...

  10. Fractional thermoelasticity

    CERN Document Server

    Povstenko, Yuriy

    2015-01-01

    This book is devoted to fractional thermoelasticity, i.e. thermoelasticity based on the heat conduction equation with differential operators of fractional order. Readers will discover how time-fractional differential operators describe memory effects and space-fractional differential operators deal with the long-range interaction. Fractional calculus, generalized Fourier law, axisymmetric and central symmetric problems and many relevant equations are featured in the book. The latest developments in the field are included and the reader is brought up to date with current research.  The book contains a large number of figures, to show the characteristic features of temperature and stress distributions and to represent the whole spectrum of order of fractional operators.  This work presents a picture of the state-of-the-art of fractional thermoelasticity and is suitable for specialists in applied mathematics, physics, geophysics, elasticity, thermoelasticity and engineering sciences. Corresponding sections of ...

  11. Infrared blocking, microwave and terahertz low-loss transmission AlN films grown on flexible polymeric substrates

    Science.gov (United States)

    Rudenko, E.; Tsybrii, Z.; Sizov, F.; Korotash, I.; Polotskiy, D.; Skoryk, M.; Vuichyk, M.; Svezhentsova, K.

    2017-04-01

    Aluminum nitride (AlN) film coatings on flexible substrates (polymeric Teflon, Mylar) have been obtained using a hybrid helicon-arc ion-plasma deposition technique with high adhesion of coatings. Studies of optical, morphological, and structural properties of AlN films have been carried out. It was found that AlN coatings on Teflon and Mylar thin-film substrates substantially suppress transmission of infrared (IR) radiation within the spectral range λ ˜ 5-20 μm at certain technological parameters and thickness of AlN. Transmission in THz regions by using quasioptics attains T ≈ 79%-95%, and losses measured in the channels within the microwave region 2 to 36 GHz are thermal conductivity of AlN, could be used as efficient blocking structures in the infrared spectral range ("infrared stealth") withdrawing the heat from filters warmed by IR radiation. At the same time, they can be used as the transparent ones in the microwave and THz regions, which can be important for low-temperature detector components of navigation, positioning, and telecommunication systems due to reducing the background noise.

  12. Microstructure and mechanical properties of stress-tailored piezoelectric AlN thin films for electro-acoustic devices

    Energy Technology Data Exchange (ETDEWEB)

    Reusch, Markus, E-mail: markus.reusch@iaf.fraunhofer.de [Laboratory for Compound Semiconductor Microsystems, IMTEK - Department of Microsystems Engineering, University of Freiburg, Georges-Koehler-Allee 103, 79110 Freiburg (Germany); Fraunhofer Institute for Applied Solid State Physics, Tullastrasse 72, 79108 Freiburg (Germany); Cherneva, Sabina [Institute of Mechanics, Bulgarian Academy of Sciences, Acad. G. Bonchev Str., Bl. 4, 1113 Sofia (Bulgaria); Lu, Yuan; Žukauskaitė, Agnė; Kirste, Lutz; Holc, Katarzyna [Fraunhofer Institute for Applied Solid State Physics, Tullastrasse 72, 79108 Freiburg (Germany); Datcheva, Maria [Institute of Mechanics, Bulgarian Academy of Sciences, Acad. G. Bonchev Str., Bl. 4, 1113 Sofia (Bulgaria); Stoychev, Dimitar [Institute of Physical Chemistry, Bulgarian Academy of Sciences, Acad. G. Bonchev Str., Bl. 11, 1113 Sofia (Bulgaria); Lebedev, Vadim [Fraunhofer Institute for Applied Solid State Physics, Tullastrasse 72, 79108 Freiburg (Germany); Ambacher, Oliver [Laboratory for Compound Semiconductor Microsystems, IMTEK - Department of Microsystems Engineering, University of Freiburg, Georges-Koehler-Allee 103, 79110 Freiburg (Germany); Fraunhofer Institute for Applied Solid State Physics, Tullastrasse 72, 79108 Freiburg (Germany)

    2017-06-15

    Highlights: • Sputtered AlN thin films with minimized intrinsic stress gradient. • Gradual increase of N{sub 2} concentration during film growth. • No degradation of AlN film properties by changing process conditions. • 2D Raman mapping of nanoindentation area. - Abstract: Nanoindentation measurements along with atomic force microscopy, X-ray diffraction, and residual stress analyses on the basis of Raman measurements have been performed to characterize stress-tailored AlN thin films grown using reactive RF magnetron sputtering. The intrinsic stress gradient caused by the growing in-plane grain size along film thickness was minimized by increasing the N{sub 2} concentration in the Ar/N{sub 2} gas mixture during the growth process. The increase of N{sub 2} concentration did not degrade the device-relevant material properties such as crystallographic orientation, surface morphology, piezoelectric response, or indentation modulus. Due to comparable crystallographic film properties for all investigated samples it was concluded that mainly the AlN crystallites contribute to the mechanical film properties such as indentation modulus and hardness, while the film stress or grain boundaries had only a minor influence. Therefore, by tailoring the stress gradient in the AlN films, device performance, fabrication yield, and the design flexibility of electro-acoustic devices can be greatly improved.

  13. X-ray absorption spectroscopy studies on magnetic tunnel junctions with AlO and AlN tunnel barriers

    International Nuclear Information System (INIS)

    Mun, B. S.; Moon, J. C.; Hong, S. W.; Kang, K. S.; Kim, K.; Kim, T. W.; Ju, H. L.

    2006-01-01

    X-ray photoelectron spectroscopy (XPS) and x-ray absorption spectroscopy (XAS) measurements of the optimized magnetic tunnel junctions (MTJs) with AlO and AlN barriers have been performed to study the chemical structures of the barrier and the underlying layer. These MTJs with AlO and AlN barriers exhibited increased tunneling magnetoresistance (TMR) after annealing at 200 deg. C from 27% to 45% and from 25% to 33%, respectively. Surprisingly, the XPS and XAS measurements confirmed that both the as-grown and the annealed MTJs had metallic Co and Fe at the interface between the barrier and the underlying CoFe layer. After annealing, under-stoichiometric AlO x and AlN x phases in MTJs with AlO and AlN barriers partially transformed into stoichiometric Al 2 O 3 and AlN phases, respectively. Thus the increase in TMR after annealing for MTJs with clean interface between the barrier and the underlying layer is believed due to the anion redistribution inside the barrier layer, not from back diffusion from pinned magnetic layer to barrier layer

  14. Acanthocephala Parasite (Profilicollis spp.) Loads in Correlation to Pacific Mole Crab (Emerita analoga) Size

    Science.gov (United States)

    Cheng, T.; Huang, S.; Galathe, M.; Jenkins, M.; Ramirez, A.; Crosby, L.; Barrera, J.; FitzHoward, S.

    2013-12-01

    Since 2002, San Francisco Bay students have been conducting marine ecosystem monitoring through a joint project with the Long-term Monitoring Program and Experiential Training for Students (LiMPETS), in conjunction with the Gulf of Farallones National Marine Sanctuary. Each year students collect population and demographic data on Pacific mole crabs (Emerita analoga), an indicator species that lives in the sandy beach habitat in temperate regions along the Pacific Ocean. Pacific mole crabs are filter feeding crustaceans that inhabit the intertidal swash zone and are known to be an intermediate host for parasitic ';spiny-headed' worms in the phylum Acanthocephala (Profilicollis spp.). Sampling takes place during their reproductive period, which occurs from spring to fall, and includes measuring total body length of the Pacific mole crabs and dissecting them to determine presence of Acanthocephalan parasites. We hypothesize that due to larger body mass, larger Pacific mole crabs will have a greater number of Acanthocephala parasites.We conducted several analyses using the LiMPETS long-term data. Specifically, we compared body length, crab gender, and parasite abundance from Pacific mole crabs sampled from four beaches located in the county and city of San Francisco. Our results indicated that larger Pacific mole crabs do not necessarily have more parasites, but are more likely to have at least one parasite, while female Pacific mole crabs carrying eggs, have more parasites than males or females without eggs. We also found that parasite loads per mole crab was highest in the spring. Further analysis will be conducted to determine factors affecting Pacific mole crab parasite loads. Studying Pacific mole crabs help evaluate the health of California's intertidal systems and how human activities, geologic changes, and climate changes all make huge impacts to the intertidal ecosystems.

  15. Potential negative effects of earthworm prey on damage to turfgrass by omnivorous mole crickets (Orthoptera: Gryllotalpidae).

    Science.gov (United States)

    Xu, Yao; Held, David W; Hu, Xing Ping

    2012-10-01

    The severity of damage to host plants by omnivorous pests can vary according to the availability of plant and animal prey. Two omnivorous mole crickets, Scapteriscus vicinus Scudder and S. borellii Giglio-Tos, were used to determine if the availability of prey influences damage to hybrid bermudagrass by adult mole crickets. Experiments were conducted in arenas with either grass alone (control), grass plus one mole cricket, grass plus earthworms (Eisenia fetida Savigny), or grass with earthworms and a mole cricket. Root growth variables (e.g., volume, dry weight) after 4 wk and weekly measurements of top growth were compared among the treatments. Surprisingly, bermudagrass infested with either mole cricket species caused no significant reduction in root growth and a minimal reduction on top growth with S. vicinus compared with controls. Survival of earthworms with S. borellii was significantly lower than survival in the earthworm-only treatment suggesting predation. Survival of earthworms with S. vicinus, however, was not different from the earthworm-only treatment. The addition of earthworm prey with mole crickets did not significantly impact bermudagrass root or shoot growth relative to grass with only mole crickets. Despite no negative impacts from earthworms or mole crickets separately, earthworms plus mole crickets negatively impact several root parameters (e.g., length) suggesting an interaction between these two soil-dwelling invertebrates. Increased use of more target-selective insecticides in turfgrass may increase available prey. This work suggests that alternative prey, when present, may result in a negative impact on turfgrass roots from foraging omnivorous mole crickets.

  16. THE CLAY CONTENT EFFECT ON THE FORMATION OF SHALLOW MOLE DRAINAGE AND THE RATE OF LOWERING SOIL MOISTURE CONTENT

    Directory of Open Access Journals (Sweden)

    Siti Suharyatun

    2014-10-01

    loam soil did not infl uence the rate of lowering soil moisture content. Contrary, the mole drainage installed in clay soil has effected to increase the rate of lowering soil moisture content. Keywords: Mole drainage, soil moisture content, clay content

  17. Enhanced Piezoelectric Response of AlN via CrN Alloying

    Science.gov (United States)

    Manna, Sukriti; Talley, Kevin R.; Gorai, Prashun; Mangum, John; Zakutayev, Andriy; Brennecka, Geoff L.; Stevanović, Vladan; Ciobanu, Cristian V.

    2018-03-01

    Since AlN has emerged as an important piezoelectric material for a wide variety of applications, efforts have been made to increase its piezoelectric response via alloying with transition metals that can substitute for Al in the wurtzite lattice. We report on density functional theory calculations of structure and properties of the Crx Al1 -x N system for Cr concentrations ranging from zero to beyond the wurtzite-rocksalt transition point. By studying the different contributions to the longitudinal piezoelectric coefficient, we propose that the physical origin of the enhanced piezoelectricity in Crx Al1 -x N alloys is the increase of the internal parameter u of the wurtzite structure upon substitution of Al with the larger Cr ions. Among a set of wurtzite-structured materials, we find that Crx Al1 -x N has the most sensitive piezoelectric coefficient with respect to alloying concentration. Based on these results, we propose that Crx Al1 -x N is a viable piezoelectric material whose properties can be tuned via Cr composition. We support this proposal by combinatorial synthesis experiments, which show that Cr can be incorporated in the AlN lattice up to 30% before a detectable transition to rocksalt occurs. At this Cr content, the piezoelectric modulus d33 is approximately 4 times larger than that of pure AlN. This finding, combined with the relative ease of synthesis under nonequilibrium conditions, may position Crx Al1 -x N as a prime piezoelectric material for applications such as resonators and acoustic wave generators.

  18. Enhanced Piezoelectric Response of AlN via CrN Alloying

    Energy Technology Data Exchange (ETDEWEB)

    Manna, Sukriti; Talley, Kevin R.; Gorai, Prashun; Mangum, John; Zakutayev, Andriy; Brennecka, Geoff L.; Stevanović, Vladan; Ciobanu, Cristian V.

    2018-03-01

    Since AlN has emerged as an important piezoelectric material for a wide variety of applications, efforts have been made to increase its piezoelectric response via alloying with transition metals that can substitute for Al in the wurtzite lattice. We report on density functional theory calculations of structure and properties of the CrxAl1-xN system for Cr concentrations ranging from zero to beyond the wurtzite-rocksalt transition point. By studying the different contributions to the longitudinal piezoelectric coefficient, we propose that the physical origin of the enhanced piezoelectricity in CrxAl1-xN alloys is the increase of the internal parameter u of the wurtzite structure upon substitution of Al with the larger Cr ions. Among a set of wurtzite-structured materials, we find that CrxAl1-xN has the most sensitive piezoelectric coefficient with respect to alloying concentration. Based on these results, we propose that CrxAl1-xN is a viable piezoelectric material whose properties can be tuned via Cr composition. We support this proposal by combinatorial synthesis experiments, which show that Cr can be incorporated in the AlN lattice up to 30% before a detectable transition to rocksalt occurs. At this Cr content, the piezoelectric modulus d33 is approximately 4 times larger than that of pure AlN. This finding, combined with the relative ease of synthesis under nonequilibrium conditions, may position CrxAl1-xN as a prime piezoelectric material for applications such as resonators and acoustic wave generators.

  19. Modeling of the Formation of AlN Precipitates During Solidification of Steel

    Directory of Open Access Journals (Sweden)

    Kalisz D.

    2013-03-01

    Full Text Available The study was carried out computer simulations of the formation process of AlN precipitates in the solidification of steel. The chemical composition of steel and non-metallic inclusions formed was determined using the commercial software FactSage. Calculated amount of precipitates formed during cooling of steel between the liquidus and solidus temperatures under conditions of thermodynamic equilibrium. In parallel, the computations were performed using your own computer program. It was found that aluminum nitride is formed at the final stage of solidification, and the condition of its formation is low oxygen content in steel.

  20. Hexagonal AlN Layers Grown on Sulfided Si(100) Substrate

    Science.gov (United States)

    Bessolov, V. N.; Gushchina, E. V.; Konenkova, E. V.; L'vova, T. V.; Panteleev, V. N.; Shcheglov, M. P.

    2018-01-01

    We have studied the influence of sulfide passivation on the initial stages of aluminum nitride (AlN)-layer nucleation and growth by hydride vapor-phase epitaxy (HVPE) on (100)-oriented single-crystalline silicon substrates. It is established that the substrate pretreatment in (NH4)2S aqueous solution leads to the columnar nucleation of hexagonal AlN crystals of two modifications rotated by 30° relative to each other. Based on the sulfide treatment, a simple method of oxide removal from and preparation of Si(100) substrate surface is developed that can be used for the epitaxial growth of group-III nitride layers.

  1. Modeling of the Formation of AlN Precipitates During Solidification of Steel

    Directory of Open Access Journals (Sweden)

    D. Kalisz

    2013-01-01

    Full Text Available The study was carried out computer simulations of the formation process of AlN precipitates in the solidification of steel. The chemical composition of steel and non-metallic inclusions formed was determined using the commercial software FactSage. Calculated amount of precipitates formed during cooling of steel between the liquidus and solidus temperatures under conditions of thermodynamic equilibrium. In parallel, the computations were performed using your own computer program. It was found that aluminum nitride is formed at the final stage of solidification, and the condition of its formation is low oxygen content in steel.

  2. Sleep in the Cape Mole Rat: A Short-Sleeping Subterranean Rodent.

    Science.gov (United States)

    Kruger, Jean-Leigh; Gravett, Nadine; Bhagwandin, Adhil; Bennett, Nigel C; Archer, Elizabeth K; Manger, Paul R

    2016-01-01

    The Cape mole rat Georychus capensis is a solitary subterranean rodent found in the western and southern Cape of South Africa. This approximately 200-gram bathyergid rodent shows a nocturnal circadian rhythm, but sleep in this species is yet to be investigated. Using telemetric recordings of the electroencephalogram (EEG) and electromyogram (EMG) in conjunction with video recordings, we were able to show that the Cape mole rat, like all other rodents, has sleep periods composed of both rapid eye movement (REM) and slow-wave (non-REM) sleep. These mole rats spent on average 15.4 h awake, 7.1 h in non-REM sleep and 1.5 h in REM sleep each day. Cape mole rats sleep substantially less than other similarly sized terrestrial rodents but have a similar percentage of total sleep time occupied by REM sleep. In addition, the duration of both non-REM and REM sleep episodes was markedly shorter in the Cape mole rat than has been observed in terrestrial rodents. Interestingly, these features (total sleep time and episode duration) are similar to those observed in another subterranean bathyergid mole rat, i.e. Fukomys mechowii. Thus, there appears to be a bathyergid type of sleep amongst the rodents that may be related to their environment and the effect of this on their circadian rhythm. Investigating further species of bathyergid mole rats may fully define the emerging picture of sleep in these subterranean African rodents. © 2016 S. Karger AG, Basel.

  3. A first-principles study of the properties of four predicted novel phases of AlN

    Science.gov (United States)

    Yang, Ruike; Zhu, Chuanshuai; Wei, Qun; Du, Zheng

    2017-05-01

    Structural, elastic, thermodynamic, electronic and optical properties of four predicted novel AlN phases (Pmn21-AlN, Pbam-AlN, Pbca-AlN and Cmcm-AlN) are calculated using first-principles according to density function theory (DFT). These phases were found using the CALYPSO method but have not yet been synthesized experimentally. Here we predict some of their properties. The properties are analyzed by means of GGA-PBE and PBE0 respectively. The more precision results are obtained by PBE0. Cmcm-AlN owns better plasticity and it's Young's modulus has clearer anisotropy than Pmn21-AlN, Pbam-AlN and Pbca-AlN. The Debye temperature, under higher temperature, shows weak temperature dependence and approach to a constant value. The Dulong-Petit limit of all four novel AlN phases and wz-AlN is about 48 J mol-1 K-1 and they have almost the same temperature law. The band structures show that the four AlN are the wide direct band gap semiconductors, which band gaps are 5.95 (Pmn21-AlN), 5.99 (Pbam-AlN), 5.88 (Pbca-AlN) and 5.59 eV (Cmcm-AlN). The bonding behaviors are the combination of covalent and ionic nature. The dielectric constants, refractive index, reflectivity, absorption, loss spectra, conductivity and Raman spectra are also calculated in detail. All four phases have a lower plasma frequency than of wz-AlN.

  4. Selective inflammatory pain insensitivity in the African naked mole-rat (Heterocephalus glaber).

    Science.gov (United States)

    Park, Thomas J; Lu, Ying; Jüttner, René; Smith, Ewan St J; Hu, Jing; Brand, Antje; Wetzel, Christiane; Milenkovic, Nevena; Erdmann, Bettina; Heppenstall, Paul A; Laurito, Charles E; Wilson, Steven P; Lewin, Gary R

    2008-01-01

    In all mammals, tissue inflammation leads to pain and behavioral sensitization to thermal and mechanical stimuli called hyperalgesia. We studied pain mechanisms in the African naked mole-rat, an unusual rodent species that lacks pain-related neuropeptides (e.g., substance P) in cutaneous sensory fibers. Naked mole-rats show a unique and remarkable lack of pain-related behaviors to two potent algogens, acid and capsaicin. Furthermore, when exposed to inflammatory insults or known mediators, naked mole-rats do not display thermal hyperalgesia. In contrast, naked mole-rats do display nocifensive behaviors in the formalin test and show mechanical hyperalgesia after inflammation. Using electrophysiology, we showed that primary afferent nociceptors in naked mole-rats are insensitive to acid stimuli, consistent with the animal's lack of acid-induced behavior. Acid transduction by sensory neurons is observed in birds, amphibians, and fish, which suggests that this tranduction mechanism has been selectively disabled in the naked mole-rat in the course of its evolution. In contrast, nociceptors do respond vigorously to capsaicin, and we also show that sensory neurons express a transient receptor potential vanilloid channel-1 ion channel that is capsaicin sensitive. Nevertheless, the activation of capsaicin-sensitive sensory neurons in naked mole-rats does not produce pain-related behavior. We show that capsaicin-sensitive nociceptors in the naked mole-rat are functionally connected to superficial dorsal horn neurons as in mice. However, the same nociceptors are also functionally connected to deep dorsal horn neurons, a connectivity that is rare in mice. The pain biology of the naked mole-rat is unique among mammals, thus the study of pain mechanisms in this unusual species can provide major insights into what constitutes "normal" mammalian nociception.

  5. Selective inflammatory pain insensitivity in the African naked mole-rat (Heterocephalus glaber.

    Directory of Open Access Journals (Sweden)

    Thomas J Park

    2008-01-01

    Full Text Available In all mammals, tissue inflammation leads to pain and behavioral sensitization to thermal and mechanical stimuli called hyperalgesia. We studied pain mechanisms in the African naked mole-rat, an unusual rodent species that lacks pain-related neuropeptides (e.g., substance P in cutaneous sensory fibers. Naked mole-rats show a unique and remarkable lack of pain-related behaviors to two potent algogens, acid and capsaicin. Furthermore, when exposed to inflammatory insults or known mediators, naked mole-rats do not display thermal hyperalgesia. In contrast, naked mole-rats do display nocifensive behaviors in the formalin test and show mechanical hyperalgesia after inflammation. Using electrophysiology, we showed that primary afferent nociceptors in naked mole-rats are insensitive to acid stimuli, consistent with the animal's lack of acid-induced behavior. Acid transduction by sensory neurons is observed in birds, amphibians, and fish, which suggests that this tranduction mechanism has been selectively disabled in the naked mole-rat in the course of its evolution. In contrast, nociceptors do respond vigorously to capsaicin, and we also show that sensory neurons express a transient receptor potential vanilloid channel-1 ion channel that is capsaicin sensitive. Nevertheless, the activation of capsaicin-sensitive sensory neurons in naked mole-rats does not produce pain-related behavior. We show that capsaicin-sensitive nociceptors in the naked mole-rat are functionally connected to superficial dorsal horn neurons as in mice. However, the same nociceptors are also functionally connected to deep dorsal horn neurons, a connectivity that is rare in mice. The pain biology of the naked mole-rat is unique among mammals, thus the study of pain mechanisms in this unusual species can provide major insights into what constitutes "normal" mammalian nociception.

  6. Low oxidation state aluminum-containing cluster anions: Cp(∗)AlnH(-), n = 1-3.

    Science.gov (United States)

    Zhang, Xinxing; Ganteför, Gerd; Eichhorn, Bryan; Mayo, Dennis; Sawyer, William H; Gill, Ann F; Kandalam, Anil K; Schnöckel, Hansgeorg; Bowen, Kit

    2016-08-21

    Three new, low oxidation state, aluminum-containing cluster anions, Cp*AlnH(-), n = 1-3, were prepared via reactions between aluminum hydride cluster anions, AlnHm (-), and Cp*H ligands. These were characterized by mass spectrometry, anion photoelectron spectroscopy, and density functional theory based calculations. Agreement between the experimentally and theoretically determined vertical detachment energies and adiabatic detachment energies validated the computed geometrical structures. Reactions between aluminum hydride cluster anions and ligands provide a new avenue for discovering low oxidation state, ligated aluminum clusters.

  7. Erratic Dislocations within Funnel Defects in AlN Templates for AlGaNEpitaxial Layer Growth

    Energy Technology Data Exchange (ETDEWEB)

    Hawkridge, Michael E; Liliental-Weber, Zuzanna; Jin Kim, Hee; Choi, Suk; Yoo, Dongwon; Ryou, Jae-Hyun; Dupuis, Russel D

    2009-03-13

    We report our transmission electron microscopy observations of erraticdislocation behavior within funnel-like defects in the top of AlN templates filled withAlGaN from an overlying epitaxial layer. This dislocation behavior is observed inmaterial where phase separation is also observed. Several bare AlN templates wereexamined to determine the formation mechanism of the funnels. Our results suggest that they are formed prior to epitaxial layer deposition due to the presence of impuritiesduring template re-growth. We discuss the erratic dislocation behavior in relation to thepresence of the phase-separated material and the possible effects of these defects on the optoelectronic properties.

  8. DETECTION OF HLA-E,-F,-G EXPRESSION ON PLACENTAL TROPHOBLASTS IN COMPLETE HYDATIDIFORM MOLE

    OpenAIRE

    正武, 孝規; 下嶋, 典子; 中西, 真理; 大村, 素子; 粕田, 承吾; 石谷, 昭子; 羽竹, 勝彦; 徳井, 宏; 林, 行夫

    2006-01-01

    In this study, we focused on HLA-E, -F and -G expression on placental trophoblasts in complete hydatidiform mole comparing these cells with early normal pregnancy. Five normal placentas at 7-9 weeks and 4 complete hydatidiform moles were tested for the expression of HLA-E, -F and -G by immunohistochemical staining using anti HLA-E, -F and -G antibodies (3D12, 3D11, and 87G). The expression of HLA-E in hydatidiform mole was slightly stronger than in early normal placentas, while the expression...

  9. Is evolution of blind mole rats determined by climate oscillations?

    Directory of Open Access Journals (Sweden)

    Yarin Hadid

    Full Text Available The concept of climate variability facilitating adaptive radiation supported by the "Court Jester" hypothesis is disputed by the "Red Queen" one, but the prevalence of one or the other might be scale-dependent. We report on a detailed, comprehensive phylo-geographic study on the ∼4 kb mtDNA sequence in underground blind mole rats of the family Spalacidae (or subfamily Spalacinae from the East Mediterranean steppes. Our study aimed at testing the presence of periodicities in branching patterns on a constructed phylogenetic tree and at searching for congruence between branching events, tectonic history and paleoclimates. In contrast to the strong support for the majority of the branching events on the tree, the absence of support in a few instances indicates that network-like evolution could exist in spalacids. In our tree, robust support was given, in concordance with paleontological data, for the separation of spalacids from muroid rodents during the first half of the Miocene when open, grass-dominated habitats were established. Marine barriers formed between Anatolia and the Balkans could have facilitated the separation of the lineage "Spalax" from the lineage "Nannospalax" and of the clade "leucodon" from the clade "xanthodon". The separation of the clade "ehrenbergi" occurred during the late stages of the tectonically induced uplift of the Anatolian high plateaus and mountains, whereas the separation of the clade "vasvarii" took place when the rapidly uplifting Taurus mountain range prevented the Mediterranean rainfalls from reaching the Central Anatolian Plateau. The separation of Spalax antiquus and S. graecus occurred when the southeastern Carpathians were uplifted. Despite the role played by tectonic events, branching events that show periodicity corresponding to 400-kyr and 100-kyr eccentricity bands illuminate the important role of orbital fluctuations on adaptive radiation in spalacids. At the given scale, our results supports the

  10. Tourism potentials of Mole National Park in Northern Ghana

    Directory of Open Access Journals (Sweden)

    Conrad Wuleka Kuuder

    2012-01-01

    Full Text Available Poor access and long distances from major cities/towns have always been major problems debarring the full utilization of nature-related touristic resources. Despite this, some adventuresome tourists still make efforts to such wildlife sanctuaries to have a feel of nature. This study explores tourism exploits at Mole National Park (the largest in Ghana which is located in the northern sector of the country. An inventory of facilities through field visits and observations were ‘exacted’ to identify different types of landforms, species of wildlife, vegetation and culture which were of touristic significance around the Park and also to have an overview of tourists’ “traffic” to the Park. With regard to data collection, the questionnaire method including personal observation were employed to obtain information from the four communities that surround the Park, the Park officials and tourists who visited the facility from April to May, 2011. The results analysed revealed that turn out was comparatively low due to the remote location of the Park including poor accessibility and low income among Ghanaians. Tourism awareness among community members was found to be high. Tourists found the Park impressive in terms of its variety in wildlife and services rendered therein. It was discovered that the Park has a high tourism potential which can be harnessed to attract both domestic and international tourists and bring socio-economic benefits to Ghana. The paper suggests that improvements in road network to and in the Park and stiffer sanctions to curb poaching were major ways to enhance tourism/recreation in the Park and making it sustainable.

  11. Assessment of Visitor Satisfaction in Mole National Park, Ghana

    Directory of Open Access Journals (Sweden)

    Conrad-J.Wuleka Kuuder

    2013-01-01

    Full Text Available Arrivals to Mole National Park (MNP, the largest in Ghana were projected by management to reach 100,000 guests by the close of2010. As at the end of December 2008, the park recorded only 16, 807 guest arrivals, the highest so far in its existence. By the close of year 2010, only 14,336 tourist arrivals were recorded registering a drop, hence an illusion in attaining the2010 set target and even subsequent years to come. This therefore gave a clue that revenue generated is not always enough to support park administration and community development. This paper explores the underlying reasons accounting for this trend by finding out tourists’ preferences in the park, the category of people who patronized the park most and sourcing guest views on what can be done to make the park more attractive. A five month period was used to elicit information from498 tourists who visited the Park employing questionnaire administration and interview schedules. The results analyzed revealed that student groups in second cycle and tertiary institutions patronized the park most on the domestic front, whilst on the foreign front, all guests contacted were educated above high school level and many of them (57% were on holiday in Ghana. The driving force (motivation behind these visits was to see animals in the wild. The most preferred wildlife species visitors came to view were elephants, monkeys, lions, buffalo and birds respectively. The recommendation is made that the road linking major cities and towns to the Park which is “rough and rugged” be rehabilitated if government needs to improve tourists’ inflow to the park.

  12. Respiration and Heartbeat Measurement for Sleep Monitoring Using a Flexible AlN Piezoelectric Film Sensor

    Directory of Open Access Journals (Sweden)

    Nan BU

    2009-11-01

    Full Text Available Respiratory and heartbeat monitoring during sleep provides basic physiological information for diagnosis of sleep disorders. This paper proposes a new method for non-invasive and unconstrained measurement of respiration and heartbeat during sleep. A flexible piezoelectric film sensor made of aluminum nitride (AlN material is used for signal acquisition. The total thickness of this sensor is less than 40 μm; the thin thickness makes it imperceptible when integrated into a bed. In addition, the AlN film sensor has good sensitivity, so that pressure fluctuation due to respiration and heartbeat can be measured when a subject is lying on this sensor. The pressure fluctuation measured can be further separated into signals corresponding to respiration and heartbeat, respectively. In the proposed method, the signal separation is achieved using an algorithm based on empirical mode decomposition (EMD. From the experimental results, it was found that respiration and heartbeat signals can be successfully obtained with the proposed method.

  13. Micromachining of AlN and Al2O3 Using Fiber Laser

    Directory of Open Access Journals (Sweden)

    Florian Preusch

    2014-11-01

    Full Text Available We report on high precision high speed micromachining of Al2O3 and AlN using pulsed near infrared fiber laser. Ablation thresholds are determined to be 30 J/cm2 for alumina and 18 J/cm2 for aluminum nitride. The factors influencing the efficiency and quality of 3D micromachining, namely the surface roughness, the material removal rate and the ablation depth accuracy are determined as a function of laser repetition rate and pulse overlap. Using a fluence of 64 J/cm², we achieve a material removal rate of up to 94 mm³/h in Al2O3 and 135 mm³/h in AlN for high pulse overlaps (89% and 84%. A minimum roughness of 1.5 μm for alumina and 1.65 μm for aluminum nitride can be accomplished for medium pulse overlaps (42% to 56%. In addition, ablation depth deviation of the micromachining process of smaller than 8% for alumina and 2% for aluminum nitride are achieved. Based on these results, by structuring exemplarily 3D structures we demonstrate the potential of high quality and efficient 3D micromachining using pulsed fiber laser.

  14. Research on the Piezoelectric Properties of AlN Thin Films for MEMS Applications

    Directory of Open Access Journals (Sweden)

    Meng Zhang

    2015-09-01

    Full Text Available In this paper, the piezoelectric coefficient d33 of AlN thin films for MEMS applications was studied by the piezoresponse force microscopy (PFM measurement and finite element method (FEM simulation. Both the sample without a top electrode and another with a top electrode were measured by PFM to characterize the piezoelectric property effectively. To obtain the numerical solution, an equivalent model of the PFM measurement system was established based on theoretical analysis. The simulation results for two samples revealed the effective measurement value d33-test should be smaller than the intrinsic value d33 due to the clamping effect of the substrate and non-ideal electric field distribution. Their influences to the measurement results were studied systematically. By comparing the experimental results with the simulation results, an experimental model linking the actual piezoelectric coefficient d33 with the measurement results d33-test was given under this testing configuration. A novel and effective approach was presented to eliminate the influences of substrate clamping and non-ideal electric field distribution and extract the actual value d33 of AlN thin films.

  15. Early stages of interface reactions between AlN and Ti thin films

    CERN Document Server

    Pinkas, M; Froumin, N; Pelleg, J; Dariel, M P

    2002-01-01

    The early stages of interface reactions between AlN and Ti thin films were investigated using x-ray diffractions, Auger electron spectroscopy, cross section transmission electron microscopy (XTEM), and high resolution XTEM. The AlN/Ti bilayers were deposited on a molybdenum substrate using reactive and nonreactive magnetron sputtering techniques. After deposition, the bilayers were heat treated for 1-10 h at 600 deg. C in a nitrogen atmosphere. Decomposition of the AlN layer took place at the AlN/Ti interface and its products, Al and N, reacted with Ti to produce a AlN/Al sub 3 Ti/Ti sub 2 N/Ti sub 3 Al/alpha-(Ti, Al)ss phase sequence. This phase sequence is not consistent with the Ti-Al-N phase diagram and is believed to be the outcome of the particular conditions that prevail in the thin film and correspond to a particular set of kinetic parameters. A model that explains the development of the phase sequence and predicts its evolution after prolonged heat treatments is put forward. The applicability of such...

  16. Theoretical study of physical and thermodynamic properties of AlnNm clusters*

    Science.gov (United States)

    Loukhovitski, Boris I.; Sharipov, Alexander S.; Starik, Alexander M.

    2016-11-01

    Geometrical structures and physical properties, such as collision diameter, rotational constants, characteristic vibrational temperatures, dipole moment, static isotropic polarizability, enthalpy of formation of various forms of AlnNm clusters with n = 0,...,5, m = 0,...,5, are analyzed with the usage of density functional theory. Different isomeric forms of these clusters with the isomerization energy up to 5 eV have been identified by using the original multistep heuristic algorithm that was based on semiempirical calculations, ab initio and density functional theory approaches and comprises the elements of genetic algorithms. Temperature dependencies of enthalpy, entropy and specific heat capacity have been calculated both for the individual isomers and for the Boltzmann ensemble of each class of clusters taking into account the anharmonicity of cluster vibrations and the contribution of excited electronic states of clusters. Novel criterion of the stability of isomeric forms, based on the maximal vibrational energy of the modes of cluster, has been proposed. The potentialities of the application of small AlnNm clusters as the components of energetic materials are also considered. Supplementary material in the form of one zip file available from the Journal web page at http://dx.doi.org/10.1140/epjd/e2016-70429-5

  17. DLC and AlN thin films influence the thermal conduction of HPLED light

    Science.gov (United States)

    Hsu, Ming Seng; Hsu, Ching Yao; Huang, Jen Wei; Shyu, Feng Lin

    2015-08-01

    Thermal dissipation had an important influence in the effect and life of light emitting diodes (LED) because it enables transfer the heat away from electric device to the aluminum plate that can be used for heat removal. In the industrial processing, the quality of the thermal dissipation decides by the gumming technique between the PCB and aluminum plate. In this study, we fabricated double layer ceramic thin films of diamond like carbon (DLC) and alumina nitride (AlN) by vacuum sputtering soldered the substrate of high power light emitting diodes (HPLED) light to check the heat conduction. The ceramic dielectric coatings were characterized by several subsequent analyses, especially the measurement of real work temperature. The X-Ray photoelectron spectroscopy (XPS) patterns reveal those ceramic phases were successfully grown onto the substrate. The work temperatures show DLC and AlN films coating had limited the heat transfer by the lower thermal conductivity of these ceramic films. Obviously, it hadn't transferred heat and limited work temperature of HPLED better than DLC thin film only.

  18. GaN growth on silane exposed AlN seed layers

    Energy Technology Data Exchange (ETDEWEB)

    Ruiz-Zepeda, F. [Posgrado en Fisica de Materiales, Centro de Investigacion Cientifica y de Educacion Superior de Ensenada, Km. 107 Carret, Tijuana-Ensenada, C.P. 22860, Ensenada, B.C. (Mexico); Contreras, O. [Centro de Ciencias de la Materia Condesada, Universidad Nacional Autonoma de Mexico, Apdo. Postal 356, C.P. 22800, Ensenada, B.C. (Mexico); Dadgar, A.; Krost, A. [Otto-von-Guericke-Universitaet Magdeburg, FNW-IEP, Universitaetsplatz 2, 39106 Magdeburg (Germany)

    2008-07-01

    The microstructure and surface morphology of GaN films grown on AlN seed layers exposed to silane flow has been studied by TEM and AFM. The epilayers were grown on silicon(111) substrates by MOCVD. The AlN seed layer surface was treated at different SiH{sub 4} exposure times prior to the growth of the GaN film. A reduction in the density of threading dislocations is observed in the GaN films and their surface roughness is minimized for an optimal SiH{sub 4} exposure time between 75-90 sec. At this optimal condition a step-flow growth mode of GaN film is predominant. The improvement of the surface and structure quality of the epilayers is observed to be related to an annihilation process of threading dislocations done by SiN{sub x} masking. (copyright 2008 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  19. Fractional charges

    International Nuclear Information System (INIS)

    Saminadayar, L.

    2001-01-01

    20 years ago fractional charges were imagined to explain values of conductivity in some materials. Recent experiments have proved the existence of charges whose value is the third of the electron charge. This article presents the experimental facts that have led theorists to predict the existence of fractional charges from the motion of quasi-particles in a linear chain of poly-acetylene to the quantum Hall effect. According to the latest theories, fractional charges are neither bosons nor fermions but anyons, they are submitted to an exclusive principle that is less stringent than that for fermions. (A.C.)

  20. Fructose-driven glycolysis supports anoxia resistance in the naked mole-rat.

    Science.gov (United States)

    Park, Thomas J; Reznick, Jane; Peterson, Bethany L; Blass, Gregory; Omerbašić, Damir; Bennett, Nigel C; Kuich, P Henning J L; Zasada, Christin; Browe, Brigitte M; Hamann, Wiebke; Applegate, Daniel T; Radke, Michael H; Kosten, Tetiana; Lutermann, Heike; Gavaghan, Victoria; Eigenbrod, Ole; Bégay, Valérie; Amoroso, Vince G; Govind, Vidya; Minshall, Richard D; Smith, Ewan St J; Larson, John; Gotthardt, Michael; Kempa, Stefan; Lewin, Gary R

    2017-04-21

    The African naked mole-rat's ( Heterocephalus glaber ) social and subterranean lifestyle generates a hypoxic niche. Under experimental conditions, naked mole-rats tolerate hours of extreme hypoxia and survive 18 minutes of total oxygen deprivation (anoxia) without apparent injury. During anoxia, the naked mole-rat switches to anaerobic metabolism fueled by fructose, which is actively accumulated and metabolized to lactate in the brain. Global expression of the GLUT5 fructose transporter and high levels of ketohexokinase were identified as molecular signatures of fructose metabolism. Fructose-driven glycolytic respiration in naked mole-rat tissues avoids feedback inhibition of glycolysis via phosphofructokinase, supporting viability. The metabolic rewiring of glycolysis can circumvent the normally lethal effects of oxygen deprivation, a mechanism that could be harnessed to minimize hypoxic damage in human disease. Copyright © 2017, American Association for the Advancement of Science.

  1. Atypical mole syndrome and dysplastic nevi: identification of populations at risk for developing melanoma - review article

    Directory of Open Access Journals (Sweden)

    Juliana Hypólito Silva

    2011-01-01

    Full Text Available Atypical Mole Syndrome is the most important phenotypic risk factor for developing cutaneous melanoma, a malignancy that accounts for about 80% of deaths from skin cancer. Because the diagnosis of melanoma at an early stage is of great prognostic relevance, the identification of Atypical Mole Syndrome carriers is essential, as well as the creation of recommended preventative measures that must be taken by these patients.

  2. Hypersensitivity to contact inhibition provides a clue to cancer resistance of naked mole-rat.

    Science.gov (United States)

    Seluanov, Andrei; Hine, Christopher; Azpurua, Jorge; Feigenson, Marina; Bozzella, Michael; Mao, Zhiyong; Catania, Kenneth C; Gorbunova, Vera

    2009-11-17

    The naked mole-rat is the longest living rodent with a maximum lifespan exceeding 28 years. In addition to its longevity, naked mole-rats have an extraordinary resistance to cancer as tumors have never been observed in these rodents. Furthermore, we show that a combination of activated Ras and SV40 LT fails to induce robust anchorage-independent growth in naked mole-rat cells, while it readily transforms mouse fibroblasts. The mechanisms responsible for the cancer resistance of naked mole-rats were unknown. Here we show that naked mole-rat fibroblasts display hypersensitivity to contact inhibition, a phenomenon we termed "early contact inhibition." Contact inhibition is a key anticancer mechanism that arrests cell division when cells reach a high density. In cell culture, naked mole-rat fibroblasts arrest at a much lower density than those from a mouse. We demonstrate that early contact inhibition requires the activity of p53 and pRb tumor suppressor pathways. Inactivation of both p53 and pRb attenuates early contact inhibition. Contact inhibition in human and mouse is triggered by the induction of p27(Kip1). In contrast, early contact inhibition in naked mole-rat is associated with the induction of p16(Ink4a). Furthermore, we show that the roles of p16(Ink4a) and p27(Kip1) in the control of contact inhibition became temporally separated in this species: the early contact inhibition is controlled by p16(Ink4a), and regular contact inhibition is controlled by p27(Kip1). We propose that the additional layer of protection conferred by two-tiered contact inhibition contributes to the remarkable tumor resistance of the naked mole-rat.

  3. The Naked Mole Rat Genome Resource : facilitating analyses of cancer and longevity-related adaptations

    OpenAIRE

    Keane, Michael; Craig, Thomas; Alfoldi, Jessica; Berlin, Aaron M; Johnson, Jeremy; Seluanov, Andrei; Gorbunova, Vera; Di Palma, Federica; Lindblad-Toh, Kerstin; Church, George M; de Magalhaes, Joao Pedro

    2014-01-01

    MOTIVATION: The naked mole rat (Heterocephalus glaber) is an exceptionally long-lived and cancer-resistant rodent native to East Africa. Although its genome was previously sequenced, here we report a new assembly sequenced by us with substantially higher N50 values for scaffolds and contigs. RESULTS: We analyzed the annotation of this new improved assembly and identified candidate genomic adaptations which may have contributed to the evolution of the naked mole rat's extraordinary traits, inc...

  4. Big insights from little animals: allosteric modulation and thermal sensitivity of shrew and mole hemoglobins

    DEFF Research Database (Denmark)

    Campbell, K.L.; Weber, Roy E.

    2007-01-01

    tissue mitochondria with sufficient O2 to fuel oxidative metabolism, such as blood with a high Bohr coefficient and half-saturation pressure (P50). However, a high P50 may drastically impede hemoglobin (Hb) saturation at low ambient PO2's and place a considerable strain on the hypoxia tolerance of shrews...... and moles. Despite these constraints, several shrew (and mole) species flourish at elevations exceeding 4500 m (where atmospheric PO2 is

  5. Management of pest mole crickets in Florida and Puerto Rico with a nematode and parasitic wasp

    International Nuclear Information System (INIS)

    Leppla, N.C.; Frank, J.H.; Adjei, M.B.; Vicente, N.E.

    2007-01-01

    Non-indigenous invasive mole crickets, Scapteriscus vicinus Scudder (Orthoptera: Gryllotalpidae) in Florida and S. didactylus (Latreille) (the 'changa') in Puerto Rico, are being managed with an entomopathogenic nematode, Steinernema scapterisci (Nguyen and Smart) (Rhabditida: Steinernematidae), and a parasitic wasp, Larra bicolor L. (Hymenoptera: Sphecidae). Pest mole cricket populations have declined by 95% in north central Florida since these specialist natural enemies were released and established in the 1980s. Commercial production of the nematode was initiated, nearly 70 billion were applied in 34 Florida counties, and their establishment, spread, and impact on mole crickets were monitored. The infected mole crickets dispersed the nematode rapidly, so that within 6 months these parasites were present in most of the insects trapped in experimental pastures. Three years later, mole cricket populations were reduced to acceptable levels and the bahiagrass had recovered. The nematode was released for the first time in Puerto Rico during 2001 and has persisted; the wasp was introduced in the late 1930s. The geographical distribution of the wasp is being expanded in Florida and Puerto Rico by planting plots of Spermacoce verticillata (L.), a wildflower indigenous to Puerto Rico and widely distributed in southern Florida. Pastures, sod farms, golf courses, landscapes, and vegetable farms in Florida and Puerto Rico are benefiting from biological control of invasive mole crickets. (author) [es

  6. High Autophagy in the Naked Mole Rat may Play a Significant Role in Maintaining Good Health

    Directory of Open Access Journals (Sweden)

    Shanmin Zhao

    2014-02-01

    Full Text Available Background/Aims: The maximum lifespan of the naked mole rat is over 28.3 years, which exceeds that of any other rodent species, suggesting that age-related changes in its body composition and functionality are either attenuated or delayed in this extraordinarily long-lived species. However, the mechanisms underlying the aging process in this species are poorly understood. In this study, we investigated whether long-lived naked mole rats display more autophagic activity than short-lived mice. Methods: Hepatic stellate cells isolated from naked mole rats were treated with 50 nM rapamycin or 20 mM 3-methyladenine (3-MA for 12 or 24 h. Expression of the autophagy marker proteins LC3-II and beclin 1 was measured with western blotting and immunohistochemistry. The induction of apoptosis was analyzed by flow cytometry. Results: Our results demonstrate that one-day-old naked mole rats have higher levels of autophagy than one-day-old short-lived C57BL/6 mice, and that both adult naked mole rats (eight months old and adult C57BL/6 mice (eight weeks old have high basal levels of autophagy, which may be an important mechanism inhibiting aging and reducing the risk of age-related diseases. Conclusion: Here, we report that autophagy facilitated the survival of hepatic stellate cells from the naked mole rat, and that treatment with 3-MA or rapamycin increased the ratio of apoptotic cells to normal hepatic stellate cells.

  7. Blunted neuronal calcium response to hypoxia in naked mole-rat hippocampus.

    Directory of Open Access Journals (Sweden)

    Bethany L Peterson

    Full Text Available Naked mole-rats are highly social and strictly subterranean rodents that live in large communal colonies in sealed and chronically oxygen-depleted burrows. Brain slices from naked mole-rats show extreme tolerance to hypoxia compared to slices from other mammals, as indicated by maintenance of synaptic transmission under more hypoxic conditions and three fold longer latency to anoxic depolarization. A key factor in determining whether or not the cellular response to hypoxia is reversible or leads to cell death may be the elevation of intracellular calcium concentration. In the present study, we used fluorescent imaging techniques to measure relative intracellular calcium changes in CA1 pyramidal cells of hippocampal slices during hypoxia. We found that calcium accumulation during hypoxia was significantly and substantially attenuated in slices from naked mole-rats compared to slices from laboratory mice. This was the case for both neonatal (postnatal day 6 and older (postnatal day 20 age groups. Furthermore, while both species demonstrated more calcium accumulation at older ages, the older naked mole-rats showed a smaller calcium accumulation response than even the younger mice. A blunted intracellular calcium response to hypoxia may contribute to the extreme hypoxia tolerance of naked mole-rat neurons. The results are discussed in terms of a general hypothesis that a very prolonged or arrested developmental process may allow adult naked mole-rat brain to retain the hypoxia tolerance normally only seen in neonatal mammals.

  8. Assessment of naked mole-rat distribution and threats in Eastern Ethiopia

    Directory of Open Access Journals (Sweden)

    Mengistu Wale

    2016-08-01

    Full Text Available Objective: To identify the distribution, threats and community attitudes towards naked molerat in Eastern Ethiopia. Methods: Data were collected through direct observation and interview and Chi-square at 95% confidence interval was used for significance test. Results: Naked mole-rat was identified in Fafan, City/Shinele, Eastern Hararghe Zone and Dire Dawa Administrative. The main threats of naked mole-rat identified were agricultural expansion, human killing and lack of awareness. From a total of 100 respondents, 92% of them considered naked mole-rat as pest as a result that 46% of them participated in direct killing. Literacy rate significantly affects the willingness to participate in the conservation of naked mole-rat (χ2 = 7.478, df = 1, P < 0.05. From a total of 26% respondents who did not show the willingness to participate in the conservation, 80.8% of them were illiterate. Conclusions: Naked mole-rat is fairly common in many of the study sites. However, rapid shift from nomadic life style to cultivation of crops and lacks of awareness were the main threats of naked mole-rat. Therefore, since there is no conservation action currently, further comprehensive study is required to design conservation plan for this species.

  9. The naked mole-rat response to oxidative stress: just deal with it.

    Science.gov (United States)

    Lewis, Kaitlyn N; Andziak, Blazej; Yang, Ting; Buffenstein, Rochelle

    2013-10-20

    The oxidative stress theory of aging has been the most widely accepted theory of aging providing insights into why we age and die for over 50 years, despite mounting evidence from a multitude of species indicating that there is no direct relationship between reactive oxygen species (ROS) and longevity. Here we explore how different species, including the longest lived rodent, the naked mole-rat, have defied the most predominant aging theory. In the case of extremely long-lived naked mole-rat, levels of ROS production are found to be similar to mice, antioxidant defenses unexceptional, and even under constitutive conditions, naked mole-rats combine a pro-oxidant intracellular milieu with high, steady state levels of oxidative damage. Clearly, naked mole-rats can tolerate this level of oxidative stress and must have mechanisms in place to prevent its translation into potentially lethal diseases. In addition to the naked mole-rat, other species from across the phylogenetic spectrum and even certain mouse strains do not support this theory. Moreover, overexpressing or knocking down antioxidant levels alters levels of oxidative damage and even cancer incidence, but does not modulate lifespan. Perhaps, it is not oxidative stress that modulates healthspan and longevity, but other cytoprotective mechanisms that allow animals to deal with high levels of oxidative damage and stress, and nevertheless live long, relatively healthy lifespans. Studying these mechanisms in uniquely long-lived species, like the naked mole-rat, may help us tease out the key contributors to aging and longevity.

  10. Blunted neuronal calcium response to hypoxia in naked mole-rat hippocampus.

    Science.gov (United States)

    Peterson, Bethany L; Larson, John; Buffenstein, Rochelle; Park, Thomas J; Fall, Christopher P

    2012-01-01

    Naked mole-rats are highly social and strictly subterranean rodents that live in large communal colonies in sealed and chronically oxygen-depleted burrows. Brain slices from naked mole-rats show extreme tolerance to hypoxia compared to slices from other mammals, as indicated by maintenance of synaptic transmission under more hypoxic conditions and three fold longer latency to anoxic depolarization. A key factor in determining whether or not the cellular response to hypoxia is reversible or leads to cell death may be the elevation of intracellular calcium concentration. In the present study, we used fluorescent imaging techniques to measure relative intracellular calcium changes in CA1 pyramidal cells of hippocampal slices during hypoxia. We found that calcium accumulation during hypoxia was significantly and substantially attenuated in slices from naked mole-rats compared to slices from laboratory mice. This was the case for both neonatal (postnatal day 6) and older (postnatal day 20) age groups. Furthermore, while both species demonstrated more calcium accumulation at older ages, the older naked mole-rats showed a smaller calcium accumulation response than even the younger mice. A blunted intracellular calcium response to hypoxia may contribute to the extreme hypoxia tolerance of naked mole-rat neurons. The results are discussed in terms of a general hypothesis that a very prolonged or arrested developmental process may allow adult naked mole-rat brain to retain the hypoxia tolerance normally only seen in neonatal mammals.

  11. Australia's first fossil marsupial mole (Notoryctemorphia) resolves controversies about their evolution and palaeoenvironmental origins.

    Science.gov (United States)

    Archer, Michael; Beck, Robin; Gott, Miranda; Hand, Suzanne; Godthelp, Henk; Black, Karen

    2011-05-22

    Fossils of a marsupial mole (Marsupialia, Notoryctemorphia, Notoryctidae) are described from early Miocene deposits in the Riversleigh World Heritage Area, northwestern Queensland, Australia. These represent the first unequivocal fossil record of the order Notoryctemorphia, the two living species of which are among the world's most specialized and bizarre mammals, but which are also convergent on certain fossorial placental mammals (most notably chrysochlorid golden moles). The fossil remains are genuinely 'transitional', documenting an intermediate stage in the acquisition of a number of specializations and showing that one of these-the dental morphology known as zalambdodonty-was acquired via a different evolutionary pathway than in placentals. They, thus, document a clear case of evolutionary convergence (rather than parallelism) between only distantly related and geographically isolated mammalian lineages-marsupial moles on the island continent of Australia and placental moles on most other, at least intermittently connected continents. In contrast to earlier presumptions about a relationship between the highly specialized body form of the blind, earless, burrowing marsupial moles and desert habitats, it is now clear that archaic burrowing marsupial moles were adapted to and probably originated in wet forest palaeoenvironments, preadapting them to movement through drier soils in the xeric environments of Australia that developed during the Neogene.

  12. Potential study of the enhanced breakdown voltage GaN MISFET based on partial AlN buried layer

    Science.gov (United States)

    Fei, Xin-Xing; Wang, Ying; Luo, Xin; Cao, Fei; Yu, Cheng-Hao

    2018-02-01

    In this paper, a new structure for GaN MISFET is proposed to enhance its breakdown voltage. The proposed structure uses an Aluminum nitride (AlN) buried layer embedded inside the GaN buffer layer. The AlN buried layer is employed to reduce the peak electric field strength near the gate, introducing a high electric field peak in the GaN buffer layer. The GaN/AlN heterojunction formed by the GaN buffer layer and the AlN buried layer introduces two electric field peaks, and enhances the uniformity of the electric field distribution in the GaN buffer layer. Simulation results of the proposed structure show that the breakdown voltage is enhanced by 78% when compared to the conventional GaN MISFET. Moreover, the specific on-resistance (Ron,sp) is improved since the AlN buried layer provides two-dimensional electron gases in the GaN buffer which can cause the charge to increase.

  13. Structural characteristics of single crystalline GaN films grown on (111) diamond with AlN buffer

    DEFF Research Database (Denmark)

    Pécz, Béla; Tóth, Lajos; Barna, Árpád

    2013-01-01

    , eliminated the inversion domains and reduced the density of threading dislocations in the GaN epilayers. The films have an in-plane epitaxial relationship [1010]GaN//[110]diamond. Thus GaN (0001) thin films of single epitaxial relationship and of single polarity were realised on diamond with AlN buffer....

  14. Crystallinity and superconductivity of as-grown MgB2 thin films with AlN buffer layers

    International Nuclear Information System (INIS)

    Tsujimoto, K.; Shimakage, H.; Wang, Z.; Kaya, N.

    2005-01-01

    The effects of aluminum nitride (AlN) buffer layers on the superconducting properties of MgB 2 thin film were investigated. The AlN buffer layers and as-grown MgB 2 thin films were deposited in situ using the multiple-target sputtering system. The best depositing condition for the AlN/MgB 2 bi-layer occurred when the AlN was deposited on c-cut sapphire substrates at 290 deg. C. The crystallinity of the AlN/MgB 2 bi-layer was studied using the XRD φ-scan and it showed that AlN and MgB 2 had the same in-plane alignment rotated at an angle of 30 deg. as compared to c-cut sapphire. The critical temperature of the MgB 2 film was 29.8 K and the resistivity was 50.0 μΩ cm at 40 K

  15. The optical properties and applications of AlN thin films prepared by a helicon sputtering system

    CERN Document Server

    Chiu, W Y; Kao, H L; Jeng, E S; Chen, J S; Jaing, C C

    2002-01-01

    AlN thin films were grown on SiO sub 2 /Si and quartz substrates using a helicon sputtering system. The dependence of film quality on growth parameters, such as total sputtering pressure, substrate temperature, and nitrogen concentration has been studied. There is a good correlation of thin film crystallinity addressed by x-ray diffraction (XRD) and spectroscopic ellipsometer. The optimized films exhibit highly oriented, with only (002) peak shown in a theta-2 theta scan XRD pattern, and extremely smooth surface with rms roughness of 2 Aa. The extinction coefficient of the film was 4x10 sup - sup 4 , which is lower than that of AlN films grown by conventional sputtering. Double-layer antireflection (DLAR) coating using AlN and Al sub 3 O sub 3 grown on quartz has been demonstrated. The transmittance of DLAR was high as 96% compared to 93% of bare substrates with the measurement error less than 0.2%. AlN films prepared by Helicon sputtering thus are potential for optical application.

  16. Fabrication and structural properties of AlN submicron periodic lateral polar structures and waveguides for UV-C applications

    Energy Technology Data Exchange (ETDEWEB)

    Alden, D. [Department of Materials Science and Engineering, North Carolina State University, Raleigh, North Carolina 27695 (United States); Institut für Festkörperphysik, Technische Universität Berlin, Hardenbergstr. 36, 10623 Berlin (Germany); Guo, W.; Kaess, F.; Bryan, I.; Reddy, P.; Hernandez-Balderrama, Luis H.; Franke, A.; Collazo, R.; Sitar, Z. [Department of Materials Science and Engineering, North Carolina State University, Raleigh, North Carolina 27695 (United States); Kirste, R.; Mita, S. [Adroit Materials, Inc., 2054 Kildaire Farm Rd., Suite 205, Cary, North Carolina 27518 (United States); Troha, T.; Zgonik, M. [Faculty of Mathematics and Physics, University of Ljubljana, Jadranska 19, 1000 Ljubljana (Slovenia); Bagal, A.; Chang, C.-H. [Department of Mechanical and Aerospace Engineering, North Carolina State University, Raleigh, North Carolina 27695 (United States); Hoffmann, A. [Institut für Festkörperphysik, Technische Universität Berlin, Hardenbergstr. 36, 10623 Berlin (Germany)

    2016-06-27

    Periodically poled AlN thin films with submicron domain widths were fabricated for nonlinear applications in the UV-VIS region. A procedure utilizing metalorganic chemical vapor deposition growth of AlN in combination with laser interference lithography was developed for making a nanoscale lateral polarity structure (LPS) with domain size down to 600 nm. The Al-polar and N-polar domains were identified by wet etching the periodic LPS in a potassium hydroxide solution and subsequent scanning electron microscopy (SEM) characterization. Fully coalesced and well-defined vertical interfaces between the adjacent domains were established by cross-sectional SEM. AlN LPSs were mechanically polished and surface roughness with a root mean square value of ∼10 nm over a 90 μm × 90 μm area was achieved. 3.8 μm wide and 650 nm thick AlN LPS waveguides were fabricated. The achieved domain sizes, surface roughness, and waveguides are suitable for second harmonic generation in the UVC spectrum.

  17. Nonpolar a-plane GaN grown on r-plane sapphire using multilayer AlN buffer by metalorganic chemical vapor deposition

    International Nuclear Information System (INIS)

    Chiang, C.H.; Chen, K.M.; Wu, Y.H.; Yeh, Y.S.; Lee, W.I.; Chen, J.F.; Lin, K.L.; Hsiao, Y.L.; Huang, W.C.; Chang, E.Y.

    2011-01-01

    Mirror-like and pit-free non-polar a-plane (1 1 -2 0) GaN films are grown on r-plane (1 -1 0 2) sapphire substrates using metalorganic chemical vapor deposition (MOCVD) with multilayer high-low-high temperature AlN buffer layers. The buffer layer structure and film quality are essential to the growth of a flat, crack-free and pit-free a-plane GaN film. The multilayer AlN buffer structure includes a thin low-temperature-deposited AlN (LT-AlN) layer inserted into the high-temperature-deposited AlN (HT-AlN) layer. The results demonstrate that the multilayer AlN buffer structure can improve the surface morphology of the upper a-plane GaN film. The grown multilayer AlN buffer structure reduced the tensile stress on the AlN buffer layers and increased the compressive stress on the a-plane GaN film. The multilayer AlN buffer structure markedly improves the surface morphology of the a-plane GaN film, as revealed by scanning electron microscopy. The effects of various growth V/III ratios was investigated to obtain a-plane GaN films with better surface morphology. The mean roughness of the surface was 1.02 nm, as revealed by atomic force microscopy. Accordingly, the multilayer AlN buffer structure improves the surface morphology and facilitates the complete coalescence of the a-plane GaN layer.

  18. The influence of sputter deposition parameters on piezoelectric and mechanical properties of AlN thin films

    International Nuclear Information System (INIS)

    Ababneh, A.; Schmid, U.; Hernando, J.; Sanchez-Rojas, J.L.; Seidel, H.

    2010-01-01

    Aluminium nitride (AlN) reactively sputter-deposited from an aluminium target is an interesting piezoelectric thin film material with high CMOS compatibility. A good c-axis orientation is essential for obtaining high piezoelectric coefficients. Therefore, the influence of different sputtering conditions on the microstructure of AlN thin films with a typical thickness of about 500 nm was investigated. In this study it is demonstrated that highly c-axis oriented AlN thin films can be deposited on nominally unheated (1 0 0) silicon substrates, most preferentially when using a pure nitrogen atmosphere. The degree of c-axis orientation increases with higher nitrogen concentration and with decreasing the sputtering pressure, whereas the influence of plasma power on the microstructure was found to be negligible. A low sputtering pressure is also useful for minimizing the amount of oxygen contaminations in the deposition chamber and hence for reducing the incorporation of impurities into the AlN films. Intrinsic stress values of AlN thin films were determined by wafer bow measurements and were found to be between -3.5 and 750 MPa depending on choice of deposition parameters. Finally, the piezoelectric coefficients d 33 and d 31 were determined experimentally by laser scanning vibrometry in conjunction with a theoretical model. Effective values in c-axis oriented 500 nm films with FWHM of 0.33 deg. are 3.0 and -1.0 pm/V. For a film of 2.4 μm thickness, values of 5.0 and -1.8 pm/V were measured, which are near the bulk values.

  19. Study of the 27Al(n,2,)26Al reaction via accelerator mass spectrometry

    International Nuclear Information System (INIS)

    Wallner, A.

    2000-06-01

    The excitation function for the 27 Al(n,2n) 26 Al reaction is expected to show a strongly non-linear behavior in the neutron-energy region around 14 MeV, the neutron energy in D-T plasmas; thus the production rate of 26 Al (t 1/2 =7.2*10 5 a) in D-T fusion environments can in principle be used to measure the temperature of such plasmas. Existing measurements, however, are strongly discordant. Therefore, a new accurate measurement of the 27 Al(n,2n) 26 Al cross sections in the near threshold region (E n =13.5-14.8 MeV) was performed with the goal to achieve relative cross sections with the highest accuracy possible. In addition, the measurements were also designed to provide good absolute cross-section values, as absolute cross sections are important for radioactive waste predictions. Samples of Al metal were irradiated with neutrons in the energy range near threshold (E th =13.55 MeV) at the Radiuminstitutes of both Vienna and St. Petersburg, and in Tokai-mura, Japan. In Tuebingen irradiations with neutrons of higher energies (17 and 19 MeV) were performed. The amount of 26 Al produced during the irradiations was measured via accelerator mass spectrometry (AMS) at the Vienna Environmental Research Accelerator (VERA). This work represents the first 26 Al measurements for this new facility. With this system, a background as low as 3*10 -15 for 26 Al/ 27 Al isotope ratios was obtained, corresponding to a (n,2n) cross section of 0.04 mb. Utilizing AMS, cross sections with much higher precision and considerably closer to the threshold than in previous investigations could be measured. The prerequisite for its application as a temperature monitor, namely a very well known shape of the excitation function was met. A quantitative prediction of the sensitivity of this method for monitoring the temperature in a D-T fusion plasma was therefore possible. For thermal plasmas temperature changes in the order of 5 to 15 % should be detectable. An even higher sensitivity was found

  20. In Situ Fabrication of AlN Coating by Reactive Plasma Spraying of Al/AlN Powder

    Directory of Open Access Journals (Sweden)

    Mohammed Shahien

    2011-10-01

    Full Text Available Reactive plasma spraying is a promising technology for the in situ formation of aluminum nitride (AlN coatings. Recently, it became possible to fabricate cubic-AlN-(c-AlN based coatings through reactive plasma spraying of Al powder in an ambient atmosphere. However, it was difficult to fabricate a coating with high AlN content and suitable thickness due to the coalescence of the Al particles. In this study, the influence of using AlN additive (h-AlN to increase the AlN content of the coating and improve the reaction process was investigated. The simple mixing of Al and AlN powders was not suitable for fabricating AlN coatings through reactive plasma spraying. However, it was possible to prepare a homogenously mixed, agglomerated and dispersed Al/AlN mixture (which enabled in-flight interaction between the powder and the surrounding plasma by wet-mixing in a planetary mill. Increasing the AlN content in the mixture prevented coalescence and increased the nitride content gradually. Using 30 to 40 wt% AlN was sufficient to fabricate a thick (more than 200 µm AlN coating with high hardness (approximately 1000 Hv. The AlN additive prevented the coalescence of Al metal and enhanced post-deposition nitriding through N2 plasma irradiation by allowing the nitriding species in the plasma to impinge on a larger Al surface area. Using AlN as a feedstock additive was found to be a suitable method for fabricating AlN coatings by reactive plasma spraying. Moreover, the fabricated coatings consist of hexagonal (h-AlN, c-AlN (rock-salt and zinc-blend phases and certain oxides: aluminum oxynitride (Al5O6N, cubic sphalerite Al23O27N5 (ALON and Al2O3. The zinc-blend c-AlN and ALON phases were attributed to the transformation of the h-AlN feedstock during the reactive plasma spraying. Thus, the zinc-blend c

  1. Emission spectra from AlN and GaN doped with rare earth elements

    International Nuclear Information System (INIS)

    Choi, Sung Woo; Emura, Shuichi; Kimura, Shigeya; Kim, Moo Seong; Zhou Yikai; Teraguchi, Nobuaki; Suzuki, Akira; Yanase, Akira; Asahi, Hajime

    2006-01-01

    Luminescent properties of GaN and AlN based semiconductors containing rare earth metals of Gd and Dy are studied. Cathodoluminescent spectra from AlGdN show a clear and sharp peak at 318 nm following LO phonon satellites. Photoluminescence spectra from GaDyN by the above-gap excitation also show several peaks in addition to the broad luminescence band emission. For GaGdN, the sharp PL peaks are also observed at 650 and 670 nm, and they are assigned to the intra-f orbital transitions by their time decay measurements. The broad band at around 365 nm for AlGdN, 505 nm for GaGdN and GaDyN are commonly observed. The origin of these broad bands is discussed

  2. Closo-alanes (Al4H4, AlnHn+2, 4 aluminum hydride chemistry.

    Science.gov (United States)

    Grubisic, A; Li, X; Stokes, S T; Cordes, J; Ganteför, G F; Bowen, K H; Kiran, B; Jena, P; Burgert, R; Schnöckel, H

    2007-05-09

    Anion photoelectron spectroscopy and density functional theory were employed to study aluminum hydride clusters, AlnHm- (4 aluminum versions of hypothetical diprotonated closo-borane dianions (BnHn2- + 2H+). In addition, Al4H4 assumes a closo-tetrahedral geometry, while Al4H6 takes on a distorted tetrahedral (D2d) structure with two counter-positioned bridging hydrogen atoms and has the largest HOMO-LUMO gap (1.9 eV) of all the alanes we studied. All of these species can be understood in terms of underlying polyhedral skeletal electron pair theory (PSEPT) concepts. Although, the herein studied alanes do not have direct borane analogues, the ability to understand their structures in terms of the Wade-Mingos rules and the underlying PSEPT concepts suggests that they can be considered as borane analogues, thereby opening a new chapter in aluminum hydride chemistry.

  3. Spin splitting in bulk wurtzite AlN under biaxial strain

    Science.gov (United States)

    Kao, Hsiu-Fen; Lo, Ikai; Chiang, Jih-Chen; Lee, Meng-En; Wu, C. L.; Wang, W. T.; Chen, Chun-Nan; Hsu, Y. C.

    2012-05-01

    The spin-splitting energies in biaxially strained bulk wurtzite material AlN are calculated using the linear combination of atomic orbital (LCAO) method, and the equi-spin-splitting distributions in k-space near the minimum-spin-splitting (MSS) surfaces are illustrated. These data are compared with those derived analytically by two-band k . p (2KP) model. It is found that the results from these two methods are in good agreement for small k. However, the ellipsoidal MSS surface under biaxial compressive strain does not exist in the 2KP model, because the data points are far from the Γ point. Instead, three basic shapes of the MSS surface occur in the wurtzite Brillouin zone: a hyperboloid of two sheets, a hexagonal cone, and a hyperboloid of one sheet, evaluated from the LCAO method across the range of biaxial strains from compressive to tensile.

  4. Electronic and atomic structure of the AlnHn+2 clusters

    DEFF Research Database (Denmark)

    Martinez, Jose Ignacio; Alonso, J.A.

    2008-01-01

    The electronic and atomic structure of the family of hydrogenated Al clusters AlnHn+2 with n=4-11 has been studied using the density functional theory with the generalized gradient approximation (GGA) for exchange and correlation. All these clusters have substantial gaps between the highest...... a polyhedron of n vertices and n H atoms form strong H-Al terminal bonds; one pair of electrons is involved in each of those bonds. The remaining n+1 electron pairs form a delocalized cloud over the surface of the Al cage. The clusters fulfilling the Wade-Mingos rule have wider HOMO-LUMO gaps...... and are chemically more stable. The trends in the gap have some reflections in the form of the photoabsorption spectra, calculated in the framework of time-dependent density functional theory using the GGA single-particle energies and orbitals and a local density approximation exchange-correlation kernel....

  5. Ion implantation of Cd and Ag into AlN and GaN

    CERN Document Server

    Miranda, Sérgio M C; Correia, João Guilherme; Vianden, Reiner; Johnston, Karl; Alves, Eduardo; Lorenz, Katharina

    2012-01-01

    GaN and AlN thin films were implanted with cadmium (Cd) or silver (Ag), to fluences ranging from 1×1013 to 1.7 × 1015 at/cm$^{2}$. The implanted samples were annealed at 950 ºC under flowing nitrogen. While implantation damage could be fully removed for the lowest fluences, for higher fluences the crystal quality was only partially recovered. For the high fluence samples the lattice site location of the ions was studied by Rutherford Backscattering/ channelling (RBS/C). Cd ions are found to be incorporated in substitutional cation sites (Al or Ga) while Ag is slightly displaced from this position. To further investigate the incorporation sites, Perturbed Angular Correlation (PAC) measurements were performed and the electric field gradients at the site of the probe nuclei were determined.

  6. Mystery Fractions

    Science.gov (United States)

    Bhattacharyya, Sonalee; Namakshi, Nama; Zunker, Christina; Warshauer, Hiroko K.; Warshauer, Max

    2016-01-01

    Making math more engaging for students is a challenge that every teacher faces on a daily basis. These authors write that they are constantly searching for rich problem-solving tasks that cover the necessary content, develop critical-thinking skills, and engage student interest. The Mystery Fraction activity provided here focuses on a key number…

  7. Central visual system of the naked mole-rat (Heterocephalus glaber).

    Science.gov (United States)

    Crish, Samuel D; Dengler-Crish, Christine M; Catania, Kenneth C

    2006-02-01

    Naked mole-rats are fossorial rodents native to eastern Africa that spend their lives in extensive subterranean burrows where visual cues are poor. Not surprisingly, they have a degenerated eye and optic nerve, suggesting they have poor visual abilities. However, little is known about their central visual system. To investigate the organization of their central visual system, we injected a neuronal tracer into the eyes of naked mole-rats and mice to compare the neural structures mediating vision. We found that the superior colliculus and lateral geniculate nucleus were severely atrophied in the naked mole-rat. The olivary pretectal nucleus was reduced but still retained its characteristic morphology, possibly indicating a role in light detection. In addition, the suprachiasmatic nucleus is well innervated and resembles the same structure in other rodents. The naked mole-rat appears to have selectively lost structures that mediate form vision while retaining structures needed for minimal entrainment of circadian rhythms. Similar results have been reported for other mole-rat species. Taken together, these data suggest that light detection may still play an important role in the lives of these "blind" animals: most likely for circadian entrainment or setting seasonal rhythms.

  8. Unraveling the message: insights into comparative genomics of the naked mole-rat.

    Science.gov (United States)

    Lewis, Kaitlyn N; Soifer, Ilya; Melamud, Eugene; Roy, Margaret; McIsaac, R Scott; Hibbs, Matthew; Buffenstein, Rochelle

    2016-08-01

    Animals have evolved to survive, and even thrive, in different environments. Genetic adaptations may have indirectly created phenotypes that also resulted in a longer lifespan. One example of this phenomenon is the preternaturally long-lived naked mole-rat. This strictly subterranean rodent tolerates hypoxia, hypercapnia, and soil-based toxins. Naked mole-rats also exhibit pronounced resistance to cancer and an attenuated decline of many physiological characteristics that often decline as mammals age. Elucidating mechanisms that give rise to their unique phenotypes will lead to better understanding of subterranean ecophysiology and biology of aging. Comparative genomics could be a useful tool in this regard. Since the publication of a naked mole-rat genome assembly in 2011, analyses of genomic and transcriptomic data have enabled a clearer understanding of mole-rat evolutionary history and suggested molecular pathways (e.g., NRF2-signaling activation and DNA damage repair mechanisms) that may explain the extraordinarily longevity and unique health traits of this species. However, careful scrutiny and re-analysis suggest that some identified features result from incorrect or imprecise annotation and assembly of the naked mole-rat genome: in addition, some of these conclusions (e.g., genes involved in cancer resistance and hairlessness) are rejected when the analysis includes additional, more closely related species. We describe how the combination of better study design, improved genomic sequencing techniques, and new bioinformatic and data analytical tools will improve comparative genomics and ultimately bridge the gap between traditional model and nonmodel organisms.

  9. Micro-Raman Investigation of Nanocrystalline GaN, AlN, and an AlGaN Composite Prepared from Pyrolysis of Metal Amide-Imide Precursors

    National Research Council Canada - National Science Library

    Coffer, J

    1998-01-01

    .... Raman spectra of nanophase aluminum nitride (AlN) and an aluminum gallium nitride (AlGaN) composite prepared from pyrolysis of the requisite precursors at a fixed temperature of 900 deg C are also presented.

  10. Improved Performance of Highly Scaled AlGaN/GaN High-Electron-Mobility Transistors Using an AlN Back Barrier

    Science.gov (United States)

    Kong, Xin; Wei, Ke; Liu, Guoguo; Liu, Xinyu; Wang, Cuimei; Wang, Xiaoliang

    2013-05-01

    An ultrathin AlN layer is inserted between the GaN channel and buffer in the fabrication of deep-submicrometer AlGaN/GaN high-electron-mobility transistors (HEMTs). The wide bandgap of AlN establishes a high back barrier and thus enhances the confinement of two-dimensional electron gas under high drain bias voltages. Owning to the effective suppression of short-channel effects in the device with a highly scaled gate length, the fabricated AlN back barrier HEMTs show better pinch-off quality, lower subthreshold current, lower drain-induced barrier lowering factor, and better high-frequency response than the reference device without an AlN back barrier.

  11. AlGaN-based deep-ultraviolet light-emitting diodes grown on high-quality AlN template using MOVPE

    KAUST Repository

    Yan, Jianchang

    2015-03-01

    In this article, we report the growth of high-quality AlN film using metal-organic vapor phase epitaxy. Three layers of middle-temperature (MT) AlN were introduced during the high-temperature (HT) AlN growth. During the MT-AlN layer growth, aluminum and nitrogen sources were closed for 6 seconds after every 5-nm MT-AlN, while H2 carrier gas was always on. The threading dislocation density in an AlN epi-layer on a sapphire substrate was reduced by almost half. AlGaN-based deep-ultraviolet light-emitting diodes were further fabricated based on the AlN/sapphire template. At 20 mA driving current, the emitted peak wavelength is 284.5 nm and the light output power exceeds 3 mW.

  12. Evaluation of the MoleMateTM training program for assessment of suspicious pigmented lesions in primary care

    Directory of Open Access Journals (Sweden)

    Annabel Wood

    2008-05-01

    Conclusion The MoleMateTM training program is a potentially effective and acceptable informatics tool to teach practitioners to recognise the features of SPLs identified by the MoleMateTM system. It will be used as part of the intervention in a randomised controlled trial to compare the diagnostic accuracy and appropriate referral rates of practitioners using the MoleMateTM system with best practice in primary care.

  13. Fractionation statistics

    OpenAIRE

    Wang, Baoyong; Zheng, Chunfang; Sankoff, David

    2011-01-01

    Abstract Background Paralog reduction, the loss of duplicate genes after whole genome duplication (WGD) is a pervasive process. Whether this loss proceeds gene by gene or through deletion of multi-gene DNA segments is controversial, as is the question of fractionation bias, namely whether one homeologous chromosome is more vulnerable to gene deletion than the other. Results As a null hypothesis, we first assume deletion events, on one homeolog only, excise a geometrically distributed number o...

  14. A Mole for Warm Magnetic and Optical Measurements of LHC Dipoles

    CERN Document Server

    Bottura, L; Deferne, G; Glöckner, C; Jansen, H; Köster, A; Legrand, P; Rijllart, A; Sievers, P

    2000-01-01

    A new rotating coil probe (a mole) has been developed for the simultaneous measurement of the magnetic field and magnetic axis of warm superconducting LHC dipoles and associated corrector windings. The mole houses a radial rotating coil and travels inside the magnet aperture by means of an externally driven two-way traction belt. The coil is rotated by an on-board piezo motor, being tested in view of future devices for cold measurements as the only type of motor compatible with strong magnetic fields. A virtual light spot is generated in the coil center by a LED source. The position of this light spot is measured from the outside by a system including a telescope, a CCD camera and a DSP. Jigs on reference granite tables are used to transfer the optical measurements to the magnet fiducials. We describe here the main characteristics and performance of the mole

  15. Twin Pregnancy with a Complete Hydatidiform Mole and a Coexisting Live Fetus; Rare entity

    Directory of Open Access Journals (Sweden)

    Shahila Sheik

    2015-11-01

    Full Text Available A hydatidiform mole with a coexisting live fetus is a rare occurrence and the optimal management for this condition is not yet known. We report the case of a 32-year-old woman (gravida 3, para 2 who presented to the Sultan Qaboos University Hospital, Muscat, Oman, in March 2012 at 13 gestational weeks with abdominal pain and vaginal bleeding. An ultrasound examination revealed a hydatidiform mole pregnancy coexisting with a live fetus. After extensive counselling, the patient and her husband opted for a conservative management approach. Unfortunately, a hysterotomy had to be performed at 17 gestational weeks due to severe haemorrhage. The postoperative period was uneventful and histopathology results confirmed one complete mole with a coexisting fetus and normal placenta. The patient’s serum β-human chorionic gonadotropin level remained normal for 18 months following her surgery.

  16. The molecular basis of acid insensitivity in the African naked mole-rat.

    Science.gov (United States)

    Smith, Ewan St John; Omerbašić, Damir; Lechner, Stefan G; Anirudhan, Gireesh; Lapatsina, Liudmila; Lewin, Gary R

    2011-12-16

    Acid evokes pain by exciting nociceptors; the acid sensors are proton-gated ion channels that depolarize neurons. The naked mole-rat (Heterocephalus glaber) is exceptional in its acid insensitivity, but acid sensors (acid-sensing ion channels and the transient receptor potential vanilloid-1 ion channel) in naked mole-rat nociceptors are similar to those in other vertebrates. Acid inhibition of voltage-gated sodium currents is more profound in naked mole-rat nociceptors than in mouse nociceptors, however, which effectively prevents acid-induced action potential initiation. We describe a species-specific variant of the nociceptor sodium channel Na(V)1.7, which is potently blocked by protons and can account for acid insensitivity in this species. Thus, evolutionary pressure has selected for an Na(V)1.7 gene variant that tips the balance from proton-induced excitation to inhibition of action potential initiation to abolish acid nociception.

  17. DEM modelling of the penetration process of the HP3 Mole

    Science.gov (United States)

    Poganski, J.; Kargl, G.; Schweiger, H.; Kömle, N.

    2015-10-01

    The NASA InSight Mission will be launched in March 2016 and will reach the surface of Mars roughly nine months later in the Elysium Region. One of the instruments on board is the HP³ Mole to measure the planetary heat flow. For this purpose it needs to penetrate five meters deep into the surface of Mars and thus offers also the possibility to analyse the soil properties. For the reconstruction of the soil behaviour and also to predict the mole performance and maximum reachable depth in advance, numerical simulations are used. The simulation of the soil during the hammering process of the HP³ Mole requires a substantial numerical effort due to the local high dynamics and large soil deformations that occur. After comparing the capability of various simulation methods (FEM, MPM and DEM) a discrete element method (DEM) was chosen.

  18. Role of immunoexpression of cyclin D1, D3, retinoblastoma (Rb mutant and clinical risk factors on complete mole as risk factors of persistent mole

    Directory of Open Access Journals (Sweden)

    Yudi M Hidayat

    2015-10-01

    Full Text Available Introduction: Changes in complete hydatidiform mole (CHM that become persistent are difficult to handle because the malignant pathogenesis of CHM is still unclear. The growth of abnormal cells in CHM is thought to be caused by cell cycle abnormalities. Some components that play a role in this phase include cyclin D and retinoblastoma (Rb. The aim of our study was to determine the role of clinical risk factors, as well as cyclin D1, cyclin D3 and Rb-protein, in the occurrence of persistent moles. Materials and Method: This study involves 68 CHM cases at Dr. Hasan Sadikin Hospital from 2007–2011. The protein expression of cyclin D1, cyclin D3, and Rb were determined by immunohistochemistry. The results were analyzed by comparing the two groups of CHM that became persistent to those that returned to normal, as determined by a Mochizuki regression curve assessment. Results: 20 cases (29% of CHM became persistent and that 48 cases (71% returned to normal. Significant clinical variables were age (p 0.05. Conclusion: There is a strong relationship between clinical risk factors of age, excessive proliferation histopathology, serum βhCG levels ≥100,000 mU/mL, cyclin D1 and Rb mutations with the incidence of persistent moles after the evacuation of the CHM. We proposed a model to predict the risks of persistent moles with a cut-off point of 2.384, which can be used as a reference for patients with CHM.

  19. Frequência de mola hidatiforme em tecidos obtidos por curetagem uterina Frequency of hydatidiform mole in tissue obtained by curettage

    Directory of Open Access Journals (Sweden)

    Andressa Biscaro

    2012-06-01

    Full Text Available OBJETIVO: Determinar a frequência de mola hidatiforme em tecidos obtidos por curetagem uterina. MÉTODOS: Estudo transversal, prospectivo e descritivo que incluiu pacientes submetidas à curetagem uterina por diagnóstico de aborto ou mola hidatiforme cujo material obtido foi encaminhado para exame anatomopatológico. Foram excluídas aquelas que não aceitaram participar da pesquisa, recusando-se a assinar o Termo de Consentimento Informado Livre e Esclarecido. Foram analisadas as seguintes variáveis: achados anatomopatológicos, idade, raça/cor, número de gestações e abortos prévios, idade gestacional no momento do diagnóstico, níveis séricos quantitativos da fração beta da gonadotrofina coriônica humana e achados ultrassonográficos. As variáveis foram empregadas para a verificação com o diagnóstico histológico, considerado o padrão-ouro. Os dados foram armazenados e analisados no software Microsoft Excel® e no programa Epi-Info, versão 6.0 (STATCALC e os resultados apresentados como frequência (porcentagem ou média±desvio padrão. Para a associação entre variáveis qualitativas foi usado o teste do χ², e admitiu-se significância estatística quando pPURPOSE: To determine the frequency of hydatiform mole in tissues obtained by curettage. METHODS: A cross-sectional, prospective and descriptive conducted on patients who underwent curretage due to a diagnosis of abortion or hydatiform mole whose material was sent for pathological examination. We excluded women who did not accept to participate and refused to sign the free informed consent form. We studied the following variables: pathological findings, age, race, number of pregnancies and previous abortions, gestational age at diagnosis, quantitative serum beta fraction of human chorionic gonadotropin and ultrasound findings. The data were compared to the to histological diagnosis, considered to be the gold standard. Data were stored and analyzed in Microsoft Excel

  20. Mechanical performance of rat, mouse and mole spring traps, and possible implications for welfare performance.

    Directory of Open Access Journals (Sweden)

    Sandra E Baker

    Full Text Available Lethal spring traps are widely used for killing small mammals in the UK. Many require government approval, based primarily on humaneness. However, mole traps and break-back traps for rats and mice are exempt; those available vary widely in price and apparent quality. The EU is considering implementing a Trapping Directive that would alter UK legislation, and a recent report advised the EU that trapping legislation should cover all trapped species and encourage improvement of traps. Mechanical trap performance is often used as an indicator of welfare impact. We examined the mechanical evidence for scope to improve the welfare standards of rat, mouse and mole spring traps. We measured mechanical performance among a range of rat, mouse and mole traps. Impact momentum values varied 6-8 fold, and clamping force values 4-5.5 fold, among traps for killing each species. There was considerable overlap in the performance of rat and mouse traps. Trap-opening angle and spring type were related to impact momentum and clamping force in traps for both species. There was no relationship between price and mechanical performance in traps for any species, except talpa mole traps. We are unable to judge the direct welfare impact of the traps tested, but rather the potential welfare threat associated with their exemption from approval. The wide variation in mechanical performance in traps for each species, overlap in performance between rat and mouse traps and increasing availability of weaker plastic rodent traps indicate considerable scope for improving the humaneness of spring traps for rats, mice and moles. We conclude that all such traps should be subject to the UK approval process. New welfare categories might improve trap standards further. Our results could also help improve rodent trap design and assist consumers in selecting more powerful traps. Many thousands of rats, mice and moles might benefit.

  1. Stress Resistance in the Naked Mole-Rat: The Bare Essentials – A Mini-Review

    Science.gov (United States)

    Lewis, Kaitlyn N.; Mele, James; Hornsby, Peter J.; Buffenstein, Rochelle

    2012-01-01

    Background Studies comparing similar-sized species with disparate longevity may elucidate novel mechanisms that abrogate aging and prolong good health. We focus on the longest living rodent, the naked mole-rat. This mouse-sized mammal lives ∼8 times longer than do mice and, despite high levels of oxidative damage evident at a young age, it is not only very resistant to spontaneous neoplasia but also shows minimal decline in age-associated physiological traits. Objectives We assess the current status of stress resistance and longevity, focusing in particular on the molecular and cellular responses to cytotoxins and other stressors between the short-lived laboratory mouse and the naked mole-rat. Results Like other experimental animal models of lifespan extension, naked mole-rat fibroblasts are extremely tolerant of a broad spectrum of cytotoxins including heat, heavy metals, DNA-damaging agents and xenobiotics, showing LD50 values between 2- and 20-fold greater than those of fibroblasts of shorter-lived mice. Our new data reveal that naked mole-rat fibroblasts stop proliferating even at low doses of toxin whereas those mouse fibroblasts that survive treatment rapidly re-enter the cell cycle and may proliferate with DNA damage. Naked mole-rat fibroblasts also show significantly higher constitutive levels of both p53 and Nrf2 protein levels and activity, and this increases even further in response to toxins. Conclusion Enhanced cell signaling via p53 and Nrf2 protects cells against proliferating with damage, augments clearance of damaged proteins and organelles and facilitates the maintenance of both genomic and protein integrity. These pathways collectively regulate a myriad of mechanisms which may contribute to the attenuated aging profile and sustained healthspan of the naked mole-rat. Understanding how these are regulated may be also integral to sustaining positive human healthspan well into old age and may elucidate novel therapeutics for delaying the onset and

  2. Stress resistance in the naked mole-rat: the bare essentials - a mini-review.

    Science.gov (United States)

    Lewis, Kaitlyn N; Mele, James; Hornsby, Peter J; Buffenstein, Rochelle

    2012-01-01

    Studies comparing similar-sized species with disparate longevity may elucidate novel mechanisms that abrogate aging and prolong good health. We focus on the longest living rodent, the naked mole-rat. This mouse-sized mammal lives ~8 times longer than do mice and, despite high levels of oxidative damage evident at a young age, it is not only very resistant to spontaneous neoplasia but also shows minimal decline in age-associated physiological traits. We assess the current status of stress resistance and longevity, focusing in particular on the molecular and cellular responses to cytotoxins and other stressors between the short-lived laboratory mouse and the naked mole-rat. Like other experimental animal models of lifespan extension, naked mole-rat fibroblasts are extremely tolerant of a broad spectrum of cytotoxins including heat, heavy metals, DNA-damaging agents and xenobiotics, showing LD(50) values between 2- and 20-fold greater than those of fibroblasts of shorter-lived mice. Our new data reveal that naked mole-rat fibroblasts stop proliferating even at low doses of toxin whereas those mouse fibroblasts that survive treatment rapidly re-enter the cell cycle and may proliferate with DNA damage. Naked mole-rat fibroblasts also show significantly higher constitutive levels of both p53 and Nrf2 protein levels and activity, and this increases even further in response to toxins. Enhanced cell signaling via p53 and Nrf2 protects cells against proliferating with damage, augments clearance of damaged proteins and organelles and facilitates the maintenance of both genomic and protein integrity. These pathways collectively regulate a myriad of mechanisms which may contribute to the attenuated aging profile and sustained healthspan of the naked mole-rat. Understanding how these are regulated may be also integral to sustaining positive human healthspan well into old age and may elucidate novel therapeutics for delaying the onset and progression of physiological declines

  3. Extended longevity of reproductives appears to be common in Fukomys mole-rats (Rodentia, Bathyergidae.

    Directory of Open Access Journals (Sweden)

    Philip Dammann

    Full Text Available African mole-rats (Bathyergidae, Rodentia contain several social, cooperatively breeding species with low extrinsic mortality and unusually high longevity. All social bathyergids live in multigenerational families where reproduction is skewed towards a few breeding individuals. Most of their offspring remain as reproductively inactive "helpers" in their natal families, often for several years. This "reproductive subdivision" of mole-rat societies might be of interest for ageing research, as in at least one social bathyergid (Ansell's mole-rats Fukomys anselli, breeders have been shown to age significantly slower than non-breeders. These animals thus provide excellent conditions for studying the epigenetics of senescence by comparing divergent longevities within the same genotypes without the inescapable short-comings of inter-species comparisons. It has been claimed that many if not all social mole-rat species may have evolved similar ageing patterns, too. However, this remains unclear on account of the scarcity of reliable datasets on the subject. We therefore analyzed a 20-year breeding record of Giant mole-rats Fukomys mechowii, another social bathyergid species. We found that breeders indeed lived significantly longer than helpers (ca. 1.5-2.2fold depending on the sex, irrespective of social rank or other potentially confounding factors. Considering the phylogenetic positions of F. mechowii and F. anselli and unpublished data on a third Fukomys-species (F. damarensis showing essentially the same pattern, it seems probable that the reversal of the classic trade-off between somatic maintenance and sexual reproduction is characteristic of the whole genus and hence of the vast majority of social mole-rats.

  4. O2 binding and CO2 sensitivity in haemoglobins of subterranean African mole rats

    DEFF Research Database (Denmark)

    Weber, Roy E.; Jarvis, Jennifer U. M.; Fago, Angela

    2017-01-01

    Inhabiting deep and sealed subterranean burrows, mole rats exhibit a remarkable suite of specializations, including eusociality (living in colonies with single breeding queens), extraordinary longevity, cancer immunity and poikilothermy, and extreme tolerance of hypoxia and hypercapnia. With little...... and 2,3-diphosphoglycerate (DPG, the major allosteric modulator of Hb-O2 affinity in red blood cells) in four social and two solitary species of African mole rats (family Bathyergidae) originating from different biomes and soil types across Central and Southern Africa. We found no consistent patterns...

  5. Twin pregnancy with both complete hydatiform mole and coexistent alive fetus: Case report

    Directory of Open Access Journals (Sweden)

    Achour Radhouane

    2015-12-01

    Full Text Available Twin pregnancy consisting of a complete hydatidiform mole coexisting with a live fetus is a rare condition with an incidence of 1 in 22000 to 1 in 100000 pregnancies. Clinical information is limited and management is difficult due to the risk of pregnancy complications such as fetal death, vaginal bleeding, preeclampsia, hyperthyroidism, and the risk of persistent gestational trophoblastic disease. Thus, the report described about the change of size and implantation site of the molar mass coexisting with a live fetus is rare especially about sonographic findings such as echo patterns. Recently we experienced a case of complete hydatidiform mole with a healthy infant delivered at term.

  6. Generating Tunable Magnetism in AlN Nanoribbons Using Anion/Cation Vacancies:a First-Principles Prediction

    Science.gov (United States)

    Chegeni, Mahdieh; Beiranvand, Razieh; Valedbagi, Shahoo

    2017-04-01

    Using first-principles approach, we theoretically study the effect of anion/cation vacancies on structural and electro-magnetic properties of zigzag AlN nanoribbons (ZAlNNRs). Calculations were performed using a full spin-polarized method within the density functional theory (DFT). Our findings shed light on how the edge states combined with vacancy engineering can affect electro-magnetic properties of ZAlNNRs. We found that depending on the nature and number of vacancies, ZAlNNRs can design as half-metal or semiconductor. Our results reveal a significant amount of spin magnetic moment for ZAlNNR with Al vacancies (VAl). These results may open new applications of AlN nano-materials in spintronics.

  7. Effect of nanostructured AlN coatings on the oxidation-resistant properties of optical diamond films

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, H. [Physics Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States)]. E-mail: zhangh@ornl.gov; Liu, J.M. [School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083 (China); Lu, F.X. [School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083 (China)

    2007-01-30

    Diamond film is an ultra-durable optical material with high thermal conductivity and good transmission in near-infrared and far-IR (8-14 {mu}m) wavebands. CVD diamond is subjected to oxidation at temperature higher than 780 deg. C bared in air for 3 min, while it can be protected from oxidation for extended exposure in air at temperature up to 900 deg. C by a coating of aluminum nitride. Highly oriented AlN coatings were prepared for infrared windows on diamond films by reactive sputtering method and the average surface roughness (R {sub a}) of the coatings was about 10 nm. The deposited films were characterized by X-ray diffraction (XRD) and atom force microscope (AFM). XRD confirmed the preferential orientation nature and AFM showed nanostructures. Optical properties of diamond films coated AlN thin film was investigated using infrared spectrum (IR) compared with that for as-grown diamond films.

  8. A piezoelectric gyroscope based on thickness-shear modes of an AlN bimorph with inclined c-axes

    Science.gov (United States)

    Cui, Jing; Du, Jianke; Wang, Ji; Yang, Jiashi

    2014-07-01

    We propose a new structure for piezoelectric gyroscope application. It consists of a two-layered plate of AlN with inclined c-axes. Through a theoretical analysis, it is shown that when the plate is electrically driven into thickness-shear (TSh) vibration in one direction and is rotating about the plate normal, the rotation causes a TSh vibration in a perpendicular direction with an electrical output which can be used to measure the angular rate of the rotation. Since AlN can be made into thin film devices much smaller than conventional crystal acoustic wave devices, the proposed gyroscope can be made much smaller than existing piezoelectric gyroscopes. The structure can also work with other crystals of class 6mm such as ZnO and polarized ceramics.

  9. Stimulated emission and optical gain in AlGaN heterostructures grown on bulk AlN substrates

    Energy Technology Data Exchange (ETDEWEB)

    Guo, Wei, E-mail: wguo2@ncsu.edu; Bryan, Zachary; Kirste, Ronny; Bryan, Isaac; Hussey, Lindsay; Bobea, Milena; Haidet, Brian; Collazo, Ramón; Sitar, Zlatko [Department of Materials Science and Engineering, North Carolina State University, Raleigh, North Carolina 27695-7919 (United States); Xie, Jinqiao; Mita, Seiji [HexaTech, Inc., 991 Aviation Pkwy, Suite 800, Morrisville, North Carolina 27560 (United States); Gerhold, Michael [Engineering Science Directorate, Army Research Office, P.O. BOX 12211, Research Triangle Park, North Carolina 27703 (United States)

    2014-03-14

    Optical gain spectra for ∼250 nm stimulated emission were compared in three different AlGaN-based structures grown on single crystalline AlN substrates: a single AlGaN film, a double heterostructure (DH), and a Multiple Quantum Well (MQW) structure; respective threshold pumping power densities of 700, 250, and 150 kW/cm{sup 2} were observed. Above threshold, the emission was transverse-electric polarized and as narrow as 1.8 nm without a cavity. The DH and MQW structures showed gain values of 50–60 cm{sup −1} when pumped at 1 MW/cm{sup 2}. The results demonstrated the excellent optical quality of the AlGaN-based heterostructures grown on AlN substrates and their potential for realizing electrically pumped sub-280 nm laser diodes.

  10. Investigation and Characterization of Defects in Epitaxial Films for Ultraviolet Light Emitting Devices Using FUV Time-Resolved Photoluminescence, Time-Resolved Cathodoluminescence, and Spatio-Time-Resolved Cathodoluminescence Excited Using Femtosecond Laser Pulses

    Science.gov (United States)

    2013-05-22

    STRCL system. Introduction: Aluminium nitride (AlN) and high AlN mole fraction AlxGa1-xN alloys have attracted considerable interest for...resolution of approximately 10 ps. (7) STRCL studies on local exciton dynamics of a freestanding GaN substrate grown by hydride vapor phase...Namita, S. Nagao, K. Fujito, and A. Uedono, "Spatio-time-resolved cathodoluminescence studies on freestanding GaN substrates grown by hydride vapor

  11. Cu-doped AlN: A possible spinaligner at room-temperature grown by molecular beam epitaxy?

    Science.gov (United States)

    Ganz, P. R.; Schaadt, D. M.

    2011-12-01

    Cu-doped AlN was prepared by plasma assisted molecular beam epitaxy on C-plane sapphire substrates. The growth conditions were investigated for different Cu to Al flux ratios from 1.0% to 4.0%. The formation of Cu-Al alloys on the surface was observed for all doping level. In contrast to Cu-doped GaN, all samples showed diamagnetic behavior determined by SQUID measurements.

  12. Anisotropy of the Magnetic Susceptibility of the Alnö alkaline and carbonatite igneous complex

    Science.gov (United States)

    Andersson, M.; Almqvist, B.; Malehmir, A.; Troll, V. R.; Snowball, I.; Lougheed, B.

    2013-12-01

    The Alnö igneous complex in central Sweden is one of the largest (radius ~2.5 km) of the few well-known alkaline and carbonatite ring-intrusions in the world. The lithologies span from alkaline silicate rocks (nepheline syenite, ijolite, and pyroxenite) to a range of carbonatite dykes (e.g. sövite) with variable composition. The depth extent, dip, and dip direction of the alkaline and carbonatite rocks have been inferred from surface geological mapping, and a dome-shaped magma chamber with the roof at ~2 km below the palaeosurface was inferred to have supplied steeply dipping radial dykes and (shallowly dipping) cone sheets. Recent high-resolution reflection seismic profiles and gravity and ground magnetic measurements suggest, in turn, a saucer-shaped magma chamber at ~3 km depth below present day land surface. To provide further insight into the internal flow mechanics of these dykes and into their emplacement mechanisms, we have measured the anisotropy of magnetic susceptibility (AMS). About 250 samples from 119 oriented cores were collected with a handheld drilling machine from 26 localities within the Alnö complex. Prior to preparation of discrete samples for AMS, the cores were measured for their density and for ultrasonic P- and S-wave velocities. Most of the sampling locations lie on a transect through the intrusion. Three locations have been sampled in detail, to determine the variation of AMS within individual carbonatite dykes. The AMS of samples were measured in low-field, using a KLY-2 Kappabridge. Bulk magnetic susceptibility ranges from 3.01e-5 to 2.50e-1 SI, and correlates with lithology. The sövites have the widest range of susceptibility (average 4.32e-2, with a range from 3.01e-5 to 2.50e-1 SI), whereas fenites have the lowest average susceptibility (average 2.06e-3, with a range from 9.86e-5 to 1.47e-2 SI); nepheline-syenite, ijolite and pyroxenite have susceptibilities between these two end member lithologies. Sövite consists mainly of

  13. Emerging methanol-tolerant AlN nanowire oxygen reduction electrocatalyst for alkaline direct methanol fuel cell.

    Science.gov (United States)

    Lei, M; Wang, J; Li, J R; Wang, Y G; Tang, H L; Wang, W J

    2014-08-11

    Replacing precious and nondurable Pt catalysts with cheap materials is a key issue for commercialization of fuel cells. In the case of oxygen reduction reaction (ORR) catalysts for direct methanol fuel cell (DMFC), the methanol tolerance is also an important concern. Here, we develop AlN nanowires with diameters of about 100-150 nm and the length up to 1 mm through crystal growth method. We find it is electrochemically stable in methanol-contained alkaline electrolyte. This novel material exhibits pronounced electrocatalytic activity with exchange current density of about 6.52 × 10(-8) A/cm(2). The single cell assembled with AlN nanowire cathodic electrode achieves a power density of 18.9 mW cm(-2). After being maintained at 100 mA cm(-2) for 48 h, the AlN nanowire-based single cell keeps 92.1% of the initial performance, which is in comparison with 54.5% for that assembled with Pt/C cathode. This discovery reveals a new type of metal nitride ORR catalyst that can be cheaply produced from crystal growth method.

  14. Roles of kinetics and energetics in the growth of AlN by plasma-assisted molecular beam epitaxy

    International Nuclear Information System (INIS)

    Im, I. H.; Minegishi, T.; Hanada, T.; Lee, S. W.; Cho, M. W.; Yao, T.; Oh, D. C.; Chang, J. H.

    2006-01-01

    The roles of kinetics and energetics in the growth processes of AlN on c-sapphire by plasma assisted molecular beam epitaxy are investigated by varying the growth rate from 1 to 31 A/min and the substrate temperature from 800 to 1000 .deg. C. The energetics is found to govern the growth of AlN in the low-growth rate region even at a low substrate temperature of 800 .deg. C owing to the enhanced residence time of adatoms, thereby increasing the surface migration length. As the growth rate increases, the growth tends to be governed by kinetics because of a reduction in the residence time of adatoms. Consequently, the surface roughness and crystal quality are greatly improved for the low-growth-rate case. In addition, the lattice strain relaxation is completed from the beginning of epitaxy for energetics-limiting growth while lattice strain relaxation is retarded for kinetics-limiting growth because of pre-existing partial strain relaxation. Energetics becomes more favorable as the substrate temperature is raised because of an increase in the surface diffusion length owing to an enhanced diffusion coefficient. Consequently high-crystal-quality AlN layers are grown under the energetics-limiting growth condition with a screw dislocation density of 7.4 x 10 8 cm -2 even for a thin 42-nm thick film.

  15. Radiative Properties of Ceramic Al2O3, AlN and Si3N4—II: Modeling

    Science.gov (United States)

    Yang, Peiyan; Cheng, Qiang; Zhang, Zhuomin

    2017-08-01

    In Part I of this study (Cheng et al. in Int J Thermophys 37: 62, 2016), the reflectance and transmittance of dense ceramic plates were measured at wavelengths from 0.4 μm to about 20 μm. The samples of Al2O3 and AlN are semitransparent in the wavelength region from 0.4 μm to about 7 μm, where volume scattering dominates the absorption and scattering behaviors. On the other hand, the Si3N4 plate is opaque in the whole wavelength region. In the mid-infrared region, all samples show phonon vibration bands and surface reflection appears to be strong. The present study focuses on modeling the radiative properties and uses an inverse method to obtain the scattering and absorption coefficients of Al2O3 and AlN in the semitransparent region from the measured directional-hemispherical reflectance and transmittance. The scattering coefficient is also predicted using Mie theory for comparison. The Lorentz oscillator model is applied to fit the reflectance spectra of AlN and Si3N4 from 1.6 μm to 20 μm in order to obtain their optical constants. It is found that the phonon modes for Si3N4 are much stronger in the polycrystalline sample studied here than in amorphous films reported previously.

  16. Indentation-Induced Mechanical Deformation Behaviors of AlN Thin Films Deposited on c-Plane Sapphire

    Directory of Open Access Journals (Sweden)

    Sheng-Rui Jian

    2012-01-01

    Full Text Available The mechanical properties and deformation behaviors of AlN thin films deposited on c-plane sapphire substrates by helicon sputtering method were determined using the Berkovich nanoindentation and cross-sectional transmission electron microscopy (XTEM. The load-displacement curves show the “pop-ins” phenomena during nanoindentation loading, indicative of the formation of slip bands caused by the propagation of dislocations. No evidence of nanoindentation-induced phase transformation or cracking patterns was observed up to the maximum load of 80 mN, from either XTEM or atomic force microscopy (AFM of the mechanically deformed regions. Instead, XTEM revealed that the primary deformation mechanism in AlN thin films is via propagation of dislocations on both basal and pyramidal planes. Furthermore, the hardness and Young’s modulus of AlN thin films estimated using the continuous contact stiffness measurements (CSMs mode provided with the nanoindenter are 16.2 GPa and 243.5 GPa, respectively.

  17. Structural stabilities and electronic properties of Mg28-nAln clusters: A first-principles study

    Directory of Open Access Journals (Sweden)

    Bao-Juan Lu

    2017-09-01

    Full Text Available In this paper, we have constructed the alloy configurations of Mg28-nAln by replacing atoms at various possible positions, starting from the stable structures of Mg28 and Al28 clusters. According to the symmetry of the cluster structure, the isomers of these initial structures have been screened with the congruence check, which would reduce computational hours and improve efficiency. Using the first-principles method, the structural evolution, mixing behavior and electronic properties of Mg28-nAln clusters are investigated for all compositions. We conclude that Al atoms prefer to reside in the central positions of Mg−Al clusters and Mg atoms tend to occupy the peripheral location. The negative mixing enthalpies imply the stabilities of these Mg-Al clusters and thus possible applications in catalysis and hydrogen storage materials. Among Mg28-nAln clusters, Mg24Al4, Mg21Al7, Mg14Al14, Mg26Al2 and Mg27Al1 present relatively high thermodynamic stabilities, and the electronic properties of these stable structures are discussed with the charge distributions around the Fermi level.

  18. Isotope Fractionation of Water During Evaporation Without Condensation

    International Nuclear Information System (INIS)

    Cappa, Christopher D.; Drisdell, Walter S.; Smith, Jared D.; Saykally, Richard J.; Cohen, Ronald C.

    2005-01-01

    The microscopic events engendering liquid water evaporation have received much attention over the last century, but remain incompletely understood. We present measurements of isotope fractionation occurring during free molecular evaporation from liquid microjets and show that the isotope ratios of evaporating molecules exhibit dramatic differences from equilibrium vapor values, strong variations with the solution deuterium mole fraction, and a clear temperature dependence. These results indicate the existence of an energetic barrier to evaporation and that the evaporation coefficient of water is less than unity. These new insights into water evaporation promise to advance our understanding of the processes that control the formation and lifetime of clouds in the atmosphere.

  19. Pre-evacuation hCG glycoforms in uneventful complete hydatidiform mole and persistent trophoblastic disease.

    NARCIS (Netherlands)

    Thomas, C.M.G.; Kerkmeijer, L.G.W.; Ariaens, H.J.; Steen, R. van der; Massuger, L.F.A.G.; Sweep, F.C.

    2010-01-01

    OBJECTIVE: To investigate whether the glycoform distribution patterns of human chorionic gonadotropin (hCG) obtained by chromatofocusing in pre-evacuation serum are different for patients who will eventually develop into persistent trophoblastic disease in case of complete hydatidiform mole

  20. Hydatidiform mole and fetus with normal karyotype: support of a separate entity

    DEFF Research Database (Denmark)

    Vejerslev, L O; Sunde, L; Hansen, B F

    1991-01-01

    Repetitive hydatidiform mole was observed in four pregnancies. The pregnancies presented with heavy bleeding and vomiting, but the post-evacuation courses were uncomplicated, with rapid regression of serum hCG levels. Cytogenetic investigations, analyses of restriction fragment length polymorphis...

  1. The Vital Role of Basic Mathematics in Teaching and Learning the Mole Concept

    Science.gov (United States)

    Mehrotra, Alka; Koul, Anjni

    2016-01-01

    This article focuses on the importance of activity-based teaching in understanding the mole concept and the vital role of basic mathematical operations. It describes needs-based training for teachers in a professional development programme in India. Analysis of test results before and after the training indicates that teachers improved their…

  2. A new species of Gryllotalpa mole cricket (Orthoptera: Gryllotalpidae: Gryllotalpinae) from Peninsular Malaysia.

    Science.gov (United States)

    Tan, Ming Kai; Kamaruddin, Khairul Nizam

    2016-01-19

    A new species of Gryllotalpa mole cricket (Orthoptera: Gryllotalpidae) is described from Bukit Larut, Perak, Peninsular Malaysia: Gryllotalpa permai sp. n. Acoustic analysis of the male calling songs were also provided for Gryllotalpa permai sp. n. and the morphologically similar Gryllotalpa fulvipes.

  3. Plasticity and constraints on social evolution in African mole-rats: ultimate and proximate factors.

    Science.gov (United States)

    Faulkes, Chris G; Bennett, Nigel C

    2013-05-19

    Here, we review comparative studies of African mole-rats (family Bathyergidae) to explain how constraints acting at the ultimate (environmental) and proximate (organismal) levels have led to convergent gains and losses of sociality within this extensive adaptive radiation of subterranean rodents endemic to sub-Saharan Africa. At the ultimate level, living in environments that range from mesic through to arid has led to both variation and flexibility in social organization among species, culminating in the pinnacle of social evolution in the eusocial naked and Damaraland mole-rats (Heterocephalus glaber and Fukomys damarensis). The common mole-rat (Cryptomys hottentotus) provides a model example of how plasticity in social traits exists within a single species inhabiting areas with different ecological constraint. At the proximate level, reproductive strategies and cooperative breeding may be constrained by the correlated evolution of a suite of traits including physiological suppression of reproduction, the development of physiological and morphological castes, and the mode of ovulatory control and seasonality in breeding. Furthermore, recent neurobiological advances indicate that differential patterns of neurotransmitter expression within the forebrain may underpin (and limit) either a solitary or group living/cooperative lifestyle not only in mole-rats, but also more widely among disparate mammalian taxa.

  4. case of natural queen succession in a captive colony of naked mole ...

    African Journals Online (AJOL)

    Naked mole-rats occur in large colonies where usually a single queen monopolizes reproduction. Queen succession occurs from within usually as a result of aggressive encounters with subordinate females that queue for reproductive succession following colony instability, which inevitably results in death of either the ...

  5. Comparative analysis of genome maintenance genes in naked mole rat, mouse, and human

    NARCIS (Netherlands)

    S.L. Macrae (Sheila L.); Q. Zhang (Quanwei); C. Lemetre (Christophe); I. Seim (Inge); R.B. Calder (Robert B.); J.H.J. Hoeijmakers (Jan); Y. Suh (Yousin); V.N. Gladyshev (Vadim N.); A. Seluanov (Andrei); V. Gorbunova (Vera); J. Vijg (Jan); Z.D. Zhang (Zhengdong D.)

    2015-01-01

    textabstractGenome maintenance (GM) is an essential defense system against aging and cancer, as both are characterized by increased genome instability. Here, we compared the copy number variation and mutation rate of 518 GM-associated genes in the naked mole rat (NMR), mouse, and human genomes. GM

  6. Morphological divergence of breeders and helpers in wild Damaraland mole-rat societies.

    Science.gov (United States)

    Young, Andrew J; Bennett, Nigel C

    2010-11-01

    The specialization of body shape to an individual's role within society represents a pinnacle of social evolution. Although commonplace among social insects, divergence in the body shapes of breeders and helpers has to date been documented in just one social vertebrate, the naked mole-rat, Heterocephalus glaber; an extraordinary species in which large colony size and frequent inbreeding may have favored the evolution of such specialization. Here, we present new evidence of morphological divergence between breeders and helpers in the Damaraland mole-rat, Fukomys damarensis; a much less socially extreme species that reflects an independent evolutionary origin of sociality. Using longitudinal data from wild populations, we show that dominant female Damaraland mole-rats, like many social insect queens, have a significantly more elongate body shape than subordinates. This difference arises not from a pre-existing difference in the body shapes of subordinates that do, and those that do not, become dominant, but from a modification to the growth trajectory of subordinates on dominance acquisition. Our findings reveal a wider role for morphological divergence within vertebrate societies and, as Damaraland mole-rats neither live in unusually large groups nor inbreed, suggest that circumstances favoring the evolution of such specializations may be more widespread among vertebrates than previously supposed. © 2010 The Author(s). Evolution© 2010 The Society for the Study of Evolution.

  7. Blunted behavioral and c Fos responses to acidic fumes in the African naked mole-rat.

    Science.gov (United States)

    LaVinka, Pamela Colleen; Park, Thomas J

    2012-01-01

    Acidosis in the skin triggers activation of pain pathways and behaviors indicative of pain in vertebrates. The exception is the naked mole-rat, the only known vertebrate to show physiological and behavioral insensitivity to acid pain in the skin. The goal of the present study was to determine behavioral and physiological responses of this species to airborne acidic fumes, which would be expected to affect the trigeminal pain pathway in other species. Behaviorally, naked mole-rats did not avoid fumes from moderately high concentrations of acetic acid (10 and 20%), and c Fos labeling showed no increase in activity in the trigeminal nuclei and nucleus tractus solitarius. In contrast, these concentrations triggered behavioral aversion and increased Fos activity in other laboratory rodents. For a very high concentration of acetic acid (50%), naked mole-rats showed significant avoidance behavior and increased Fos labeling in the nucleus tractus solitarius caudal region, which receives vagal chemosensory information. However, there was no increase in trigeminal labeling, and in fact, activity significantly decreased. This pattern is opposite of that associated with another irritant, ammonia fumes, which elicited an increase in trigeminal but not nucleus tractus solitarius Fos labeling, and no behavioral avoidance. Behavioral avoidance of acidic fumes, but no increased labeling in the trigeminal pain nucleus is consistent with the notion of adaptations to blunt acid pain, which would be advantageous for naked mole-rats as they normally live under chronically high levels of acidosis-inducing CO(2).

  8. Blunted behavioral and c Fos responses to acidic fumes in the African naked mole-rat.

    Directory of Open Access Journals (Sweden)

    Pamela Colleen LaVinka

    Full Text Available Acidosis in the skin triggers activation of pain pathways and behaviors indicative of pain in vertebrates. The exception is the naked mole-rat, the only known vertebrate to show physiological and behavioral insensitivity to acid pain in the skin. The goal of the present study was to determine behavioral and physiological responses of this species to airborne acidic fumes, which would be expected to affect the trigeminal pain pathway in other species. Behaviorally, naked mole-rats did not avoid fumes from moderately high concentrations of acetic acid (10 and 20%, and c Fos labeling showed no increase in activity in the trigeminal nuclei and nucleus tractus solitarius. In contrast, these concentrations triggered behavioral aversion and increased Fos activity in other laboratory rodents. For a very high concentration of acetic acid (50%, naked mole-rats showed significant avoidance behavior and increased Fos labeling in the nucleus tractus solitarius caudal region, which receives vagal chemosensory information. However, there was no increase in trigeminal labeling, and in fact, activity significantly decreased. This pattern is opposite of that associated with another irritant, ammonia fumes, which elicited an increase in trigeminal but not nucleus tractus solitarius Fos labeling, and no behavioral avoidance. Behavioral avoidance of acidic fumes, but no increased labeling in the trigeminal pain nucleus is consistent with the notion of adaptations to blunt acid pain, which would be advantageous for naked mole-rats as they normally live under chronically high levels of acidosis-inducing CO(2.

  9. Trauma and humanitarian translation in Liberia: the tale of open mole.

    Science.gov (United States)

    Abramowitz, Sharon Alane

    2010-06-01

    The focus of this paper is the intercultural process through which Open Mole and trauma-related mental illnesses are brought together in the postconflict mental health encounter. In this paper, I explore the historical dimension of this process by reviewing the history of Open Mole, and the ways in which it has been interpreted, acted on, and objectified by external observers over the last half-century. Moving into Liberia's recent war and postconflict period, I examine the process by which Open Mole is transformed from a culture-bound disorder into a local idiom of trauma, and how it has become a gateway diagnosis of PTSD-related mental illnesses, and consider how it is produced as an objectified experience of psychiatric disorder in clinical humanitarian contexts. By studying how Open Mole is transformed in the humanitarian encounter, I address the structure and teleology of the humanitarian encounter and challenge some of the foundational assumptions about cultural sensitivity and community-based mental health care in postconflict settings that are prevalent in scholarship and practice today.

  10. Reading about the Power of Music: "Mole Music" and "Children of the Stone"

    Science.gov (United States)

    Cardany, Audrey Berger

    2016-01-01

    In this article, I review two books that address the power of music for the individual and group. Both books address the benefits of making, learning, and listening to music during times of conflict. The first brief review is David McPhail's picture book "Mole Music." The second is "Children of the Stone: The Power of Music in a…

  11. The Impact of Elephants on the Woody Vegetation of Mole National ...

    African Journals Online (AJOL)

    Elephant damage on trees ≥ 2 m tall involving uprooting and main trunk breakage, as well as debarking was assessed in the upper- to middle-slope and lower-slope savannas of the elephantoccupied section of Mole National Park. Elephant damage on trees in either vegetation type was light, but varied among the ...

  12. Effects of Perennial Fires on the Woody Vegetation of Mole National ...

    African Journals Online (AJOL)

    Recurrent fires have a considerable potential to influence the structure and composition of savanna vegetation. In Mole National Park in Ghana, the policy is to burn the vegetation annually early in the dry season. This study aimed to assess the effects of these perennial fires on the trees and shrubs of the Park. To achieve ...

  13. Influence of spatial environment on maze learning in an African mole-rat

    CSIR Research Space (South Africa)

    Du Toit, L

    2012-05-01

    Full Text Available with sociality in subterranean mammals, we have a less clear understanding of the role of habitat complexity on navigational ability. We tested spatial navigational ability and memory in 12–18-month captive Natal mole-rats (Cryptomys hottentotus natalensis...

  14. Review Paper: Hydatidiform mole in Calabar, Nigeria: a ten-year ...

    African Journals Online (AJOL)

    A total of 79 patients who were managed for hydatidiform mole in University of Calabar Teaching Hospital over ten years were reviewed with the aims of establishing the incidence and assessing outcome of management. Relevant information was obtained from the case files and analyzed. The incidence of 1 in 187 of total ...

  15. A Mole in the Sole: Case Report on Eccrine Poroma | Das | Internet ...

    African Journals Online (AJOL)

    Eccrine poroma is a benign tumor which arises from the intraepidermal portion of the eccrine sweat glands. 81 year old diabetic grandma worried about her persistently uncontrolled blood sugar owing to a painless mole in the sole of right foot for 2 years. Excisional biopsy revealed a sweat duct benign eccrine poroma.

  16. Microbial associates of the southern mole cricket (Scapteriscus borellii) are highly pathogenic.

    Science.gov (United States)

    Aryal, Sudarshan K; Carter-House, Derreck; Stajich, Jason E; Dillman, Adler R

    2017-11-01

    We report the isolation and identification of seven bacterial strains and one fungal strain from dead and diseased Scapteriscus borellii mole crickets collected from a golf course in southern California. Using 16S and 18S rRNA gene sequence analysis we identified the microbes as Serratia marcescens (red), S. marcescens (white), S. marcescens (purple), Achromobacter xylosoxidans, Chryseobacterium sp., Ochrobactrum anthropi, Tsukamurella tryosinosolvens, and Beauveria bassiana. We performed a dose response curve for each of these cricket-associated microbial strains (except T. tryosinosolvens) and two other strains of S. marcescens (DB1140 and ATCC 13880). We found that all of these microbes except O. anthropi were highly pathogenic to D. melanogaster compared to the other strains of S. marcescens. Injecting the mole cricket associated strains of Serratia into flies killed all infected flies in ≤24h. For all other strains, the median time to death of injected flies varied in a dose-dependent manner. In vivo growth assessments of these microbes suggested that the host immune system was quickly overcome. We used disease tolerance curves to better understand the host-microbe interactions. Further studies are necessary to understand in mechanistic detail the virulence mechanisms of these mole cricket associated microbes and how this association may have influenced the evolution of mole cricket immunity. Copyright © 2017 Elsevier Inc. All rights reserved.

  17. The eye of the African mole-rat Cryptomys anselli : to see or not to see?

    NARCIS (Netherlands)

    Cernuda-Cernuda, R; Garcia-Fernandez, JM; Gordijn, MCM; Bovee-Geurts, PHM; DeGrip, WJ; de Grip, W.J.

    In an attempt to clarify its possible physiological role, we studied the eye of the Zambian mole rat Cryptomys anselli by light, electron and confocal microscopy using conventional staining as well as immunolabelling with rod and cone cell markers. The small eyes of Cryptomys are located

  18. Biological and biochemical properties of human chorionic gonadotropin from urine of patients with hydatidiform mole and its radioimmunoassay

    International Nuclear Information System (INIS)

    Nishimura, Ryuichiro; Hamamoto, Tamotsu; Tanabe, Keizo; Takemori, Masayuki; Ashitaka, Yoshihiko

    1981-01-01

    Human chorionic gonadotropin (hCG) was extracted and purified from the urine of four patients with hydatidiform mole. The immunological activities of the hCG-hydatidiform mole by hCG radioimmunoassay (RIA) ranged from 9,380 to 9,700 IU/mg, and the biological activities measured by the immature rat ovarian weight method ranged from 7,250 to 7,780 IU/mg. The results of the amino acid compositions of all the hCG-hydatidiform moles were practically identical with those of hCG-normal pregnancies. The carbohydrate moiety of the hCG-hydatidiform mole was also suspected to be almost similar to that of hCG-normal pregnancies by the results of their in vitro and in vivo biological activities. It was demonstrated that hCG-hydatidiform mole was composed of α and β subunits (similar to a hCG-normal pregnancy) when hCG-hydatidiform mole was separated into subunits by SDS disc electrophoresis after treatment with mercaptoethanol. The RIA system of hCG-hydatidiform mole can be established. The concentrations of hCG in sera of normal pregnant women and patients with trophoblastic diseases assayed by hCG-hydatidiform mole RIA were equivalent to those obtained by a standard hCG RIA. Hence, a standard hCG-immunoassay method used in the management of trophoblastic diseases is considered reasonable so far as the immunoantigenecity of hCG is concerned. (author)

  19. Hardness evaluation of cured urea-formaldehyde resins with different formaldehyde/urea mole ratios using nanoindentation method

    Science.gov (United States)

    Byung-Dae Park; Charles R. Frihart; Yan Yu; Adya P. Singh

    2013-01-01

    To understand the influence of formaldehyde/urea (F/U) mole ratio on the properties of urea–formaldehyde (UF) resins, this study investigated hardness of cured UF resins with different F/U mole ratios using a nanoindentation method. The traditional Brinell hardness (HB) method was also used...

  20. An Investigation into Chemical Engineering Students' Understanding of the Mole and the Use of Concrete Activities To Promote Conceptual Change.

    Science.gov (United States)

    Case, Jennifer M.; Fraser, Duncan M.

    1999-01-01

    Describes an investigation of first-year chemical engineering students' understanding of the mole concept. Finds that a series of activities designed to provide students with visual or experiential points of reference for the mole concept had a strong positive effect on student misconceptions. Contains 16 references. (Author/WRM)

  1. Effects of GaN/AlGaN/Sputtered AlN nucleation layers on performance of GaN-based ultraviolet light-emitting diodes

    Science.gov (United States)

    Hu, Hongpo; Zhou, Shengjun; Liu, Xingtong; Gao, Yilin; Gui, Chengqun; Liu, Sheng

    2017-03-01

    We report on the demonstration of GaN-based ultraviolet light-emitting diodes (UV LEDs) emitting at 375 nm grown on patterned sapphire substrate (PSS) with in-situ low temperature GaN/AlGaN nucleation layers (NLs) and ex-situ sputtered AlN NL. The threading dislocation (TD) densities in GaN-based UV LEDs with GaN/AlGaN/sputtered AlN NLs were determined by high-resolution X-ray diffraction (XRD) and cross-sectional transmission electron microscopy (TEM), which revealed that the TD density in UV LED with AlGaN NL was the highest, whereas that in UV LED with sputtered AlN NL was the lowest. The light output power (LOP) of UV LED with AlGaN NL was 18.2% higher than that of UV LED with GaN NL owing to a decrease in the absorption of 375 nm UV light in the AlGaN NL with a larger bandgap. Using a sputtered AlN NL instead of the AlGaN NL, the LOP of UV LED was further enhanced by 11.3%, which is attributed to reduced TD density in InGaN/AlInGaN active region. In the sputtered AlN thickness range of 10-25 nm, the LOP of UV LED with 15-nm-thick sputtered AlN NL was the highest, revealing that optimum thickness of the sputtered AlN NL is around 15 nm.

  2. Methods of optimization of reactive sputtering conditions of Al target during AlN films deposition

    Directory of Open Access Journals (Sweden)

    Chodun Rafal

    2015-12-01

    Full Text Available Encouraged by recent studies and considering the well-documented problems occurring during AlN synthesis, we have chosen two diagnostic methods which would enable us to fully control the process of synthesis and characterize the synthesized aluminum nitride films. In our experiment we have compared the results coming from OES measurements of plasma and circulating power characteristics of the power supply with basic features of the deposited layers. The dual magnetron system operating in AC mode was used in our studies. Processes of aluminum target sputtering were carried out in an atmosphere of a mixture of argon and nitrogen. The plasma emission spectra were measured with the use of a monochromator device. Analyses were made by comparing the positions and intensities of spectral lines of the plasma components. The results obtained allowed us to characterize the sputtering process under various conditions of gas mixture compositions as well as power distribution more precisely, which is reported in this work. The measured spectra were related to the deposition rate, the structure morphology of the films and chemical composition. Our work proved that the use of plasma OES and circulating power measurements make possible to control the process of sputtering and synthesis of deposited films in situ.

  3. Ab-initio Calculations of Accurate Electronic Properties of Wurzite AlN

    Science.gov (United States)

    Nwigboji, Ifeanyi; Malozovsky, Yuriy; Bagayoko, Diola; Bagayoko Research Group Team

    2014-03-01

    We present results from ab-initio, self consistent local density approximation (LDA) calculations of electronic and related properties of wurtzite Aluminum Nitride (w-AlN). Our non-relativistic computations employed the Ceperley and Alder LDA potential and the linear combination of atomic orbital (LCAO) formalism. The implementation of the LCAO formalism followed the Bagayoko, Zhao, and Williams' method as enhanced by Ekuma and Franklin (BZW-EF). The BZW-EF method verifiably obtains the minima of the occupied energies; these minima provide the most variationally and physically valid density functional theory (DFT) description of the ground states of materials under study. Our preliminary results for w-AlN show that w-AlN has a direct band gap of 5.82 eV at the Γ point. The preliminary energy bands were obtained with a basis set comprising 48 functions. None of the several, larger basis sets tested to date led to occupied energies lower than those obtained with the above 48. While most previous LDA calculations are 2 eV smaller or more than the experimental value of 5.9 eV that is in excellent agreement with our finding, considering the typical experimental uncertainty of 0.2 eV for absorption measurements on AlN. We also discuss our calculated density of states (DOS) and partial densities of states (pDOS).

  4. Fabrication and Dielectric Properties of AlN Filled Epoxy Nano-composites

    Energy Technology Data Exchange (ETDEWEB)

    Gao Naiui; Yu Xin; Jin Haiyun; He Bo; Dong Pu [State Key Laboratory of Electrical Insulation and Power Equipment, Xi' an Jiaotong University, Xi' an, 710049 (China); Gao Chao, E-mail: hyjin@mail.xjtu.edu.cn

    2011-10-29

    Epoxy resins were materials with excellent mechanical, electrical properties and good chemical stability. Thus, they had been used in various fields, especially in electrical and electronic application. However, because they were brittle material, the fields of application were limited. Adding nano-Aluminum Nitride (AlN) into Epoxy resins could improve the toughness of the composites, the thermal behaviors of composites could also be improved, but the influence on dielectric properties was not very clear. In this research, epoxy resin based composites were fabricated. The relationships between the dielectric properties and the nano-AlN particle content were investigated. The results showed that, both relative permittivity ({epsilon}{sub r}) and dielectric loss tangent (tan{delta}) decreased to be less than that of monolithic epoxy when nano-AlN particle content was no more than certain amount, the DC volume resistivity ({rho}{sub v}) and low frequency resistivity decreased with increasing nano-AlN content (in certain range of content). AC breakdown strength (E{sub B}) did not have an obvious tendency with nano-AlN content.

  5. Direct selective metallization of AlN ceramics induced by laser radiation

    Science.gov (United States)

    Antończak, Arkadiusz J.; Kozioł, Paweł E.; Stepak, Bogusz; Szymczyk, Patrycja; Abramski, Krzysztof M.

    2014-03-01

    Aluminum nitride (AlN) ceramics has a unique characteristic, namely the ability to form conductive structures on its surface directly by laser-induced decomposition of the base material. Various research has been carried out on obtaining low-ohmic structures depending on process parameters such as the laser power, overlap of subsequent pulses and the type of shielding gas (air, nitrogen and argon). This paper focuses on explaining which factors have the greatest impact on the resistance (resistivity) value of obtained structures. In order to explain the effect of the laser fluence (below and above the ablation threshold of aluminum nitride) on the chemical structure of the conductive layers, qualitative EDX analyses were performed. Optimization of the process allowed obtaining a resistivity of the conductive layers at a level of ρ = 0.64·10-6 Ω·m, with a thickness of aluminum up to 10 μm (sheet resistance RS = 10 mΩ/Sr). This technology can be useful in making printed circuit boards (PCB), various types of sensors as well as radio-frequency identification (RFID) and Lab-On-a-Chip (LOC) structures. This technology can also be useful for the production of metamaterials.

  6. Fabrication and Dielectric Properties of AlN Filled Epoxy Nano-composites

    International Nuclear Information System (INIS)

    Gao Naiui; Yu Xin; Jin Haiyun; He Bo; Dong Pu; Gao Chao

    2011-01-01

    Epoxy resins were materials with excellent mechanical, electrical properties and good chemical stability. Thus, they had been used in various fields, especially in electrical and electronic application. However, because they were brittle material, the fields of application were limited. Adding nano-Aluminum Nitride (AlN) into Epoxy resins could improve the toughness of the composites, the thermal behaviors of composites could also be improved, but the influence on dielectric properties was not very clear. In this research, epoxy resin based composites were fabricated. The relationships between the dielectric properties and the nano-AlN particle content were investigated. The results showed that, both relative permittivity (ε r ) and dielectric loss tangent (tanδ) decreased to be less than that of monolithic epoxy when nano-AlN particle content was no more than certain amount, the DC volume resistivity (ρ v ) and low frequency resistivity decreased with increasing nano-AlN content (in certain range of content). AC breakdown strength (E B ) did not have an obvious tendency with nano-AlN content.

  7. Distribution of vasopressin in the brain of the eusocial naked mole-rat.

    Science.gov (United States)

    Rosen, Greta J; De Vries, Geert J; Goldman, Sharry L; Goldman, Bruce D; Forger, Nancy G

    2007-02-20

    Naked mole-rats are eusocial rodents that live in large subterranean colonies in which one queen breeds with one to three males. All other animals are nonbreeding subordinates. The external features of male and female subordinates, including their genitalia, are remarkably monomorphic, as is their behavior. Because vasopressin (VP) is associated with social behaviors and sex differences in other species, its distribution in naked mole-rats was of interest. We used immunohistochemistry to examine VP in the brains of subordinate and breeding naked mole-rats of both sexes. As in other mammals, VP-immunoreactive (-ir) somata were found in the paraventricular (PVN) and supraoptic nuclei (SON) and VP-ir projections from these nuclei ran through the internal and external zone of the median eminence. However, naked mole-rats had very few VP-ir cells in the bed nucleus of the stria terminalis (BST) and none in the suprachiasmatic nucleus (SCN); the extensive network of fine-caliber VP-ir fibers usually seen in projection sites of the BST and SCN were also absent. Equally unexpected was the abundance of large-caliber VP-ir fibers in the dorsomedial septum. VP immunoreactivity was generally similar in all groups, with the exception of VP-ir cell number in the dorsomedial hypothalamus (DMH). Breeders had a population of labeled cells in the DMH that was absent, or nearly absent, in subordinates. Future studies on the function of VP in these areas are needed to determine how the atypical distribution of VP immunoreactivity relates to eusociality and the unusual physiology of naked mole-rats.

  8. Screening of Common Chromosomal Disorders in Iranian Women with Hydatidiform Mole using QF-PCR

    Directory of Open Access Journals (Sweden)

    Masoumeh Barari

    2016-11-01

    Full Text Available Abstract Background: Hydatidiform Mole is a benign trophoblastic tumor is made of ectopic preg-nancy. Abnormalities in the number or structure of chromosomes are causes of Hydatidiform Mole common numerical disorders resulted from proliferating repetitive sequences markers as called STR were studied in the region of chromosome X, Y, 13, 18 and 21. This study aimed to investigate chromosomal disorders prevalent in women with hydatidiform mole, that was performed using QF-PCR techniques. Materials and Methods: In this study, 50 women with hydatidiform mole and 80 healthy women as controls were selected. For studying the chromosomal abnormalities resulted of proliferating STR, Chromo Quant QF-PCR kit was used. Polymerase chain reaction was performed in PCR machine. Then electrophoresis was performed on Genetic Analyzer. Finally, amplified fragment were analyzed by Gene Marker software Statistical analysis was performed using SPSS version 19, and t-test. Data were expressed as mean ± SD. In this test, p <0.05 represents significant level between two groups. Results: In this study ،of 50 samples, 8 samples of 47XXY (16%, 40 samples of trisomy 21 (80% and 2 cases of trisomy 18 (4% were identified. Conclusion: Anomalies Trisomy 21 (41 ± 1.58 and 47XXY (9.62 ± 1.36 are significantly associated with mydatidiform mole disease (p <0.001. The highest percentage of samples with tri-somy 21 and 47XXY had the disease. So, it indicates that these anomalies have the highest percentage in the disease.

  9. Development of (Ti, Al)N coated cBN tool for ADI machining; ADI zai kakoyo (Ti, Al) N coated cBN kogu no kaihatsu

    Energy Technology Data Exchange (ETDEWEB)

    Shintani, K.; Sugiyama, H.; Kato, H. [Kanazawa Institute of Technology, Ishikawa (Japan); Goto, M. [Sumitomo Electric Industries, Ltd., Osaka (Japan)

    1998-06-25

    Concerning cBN tools used for machining austempered ductile cast iron (ADI), the effects of difference in the strength of cBN particles themselves on tool life and the tool life extending effects of a (Ti, Al)N coating formed on the tool surface are discussed. In the experiment, three kinds of tool materials, which are C60-F, C60-M, and C60-T, are prepared, which contain 60vol% cBN particles different in strength. The flank abrasion inhibiting effect of the coating is also studied. In this study, C60c and C20c tools are tested, built of parent materials containing 20% 1{mu}m T particles and 60% 3{mu}m T particles and coated by (Ti, Al)N. Some of the conclusions reached are outlined below. The strength of cBN particles present in the specimens exerts virtually no influence on the improvement of flank abrasion characteristics. In a tool provided with a (Ti, Al)N coating, some of the (Ti, Al)N coating is retained between the cutting face near the cutting edge and the flank lower edge, and this suppresses the progress of flank abrasion. A tool provided with a (Ti, Al)N coating has a life which is more than three times the life of uncoated cBN tools. 9 refs., 12 figs., 2 tabs.

  10. MOVPE growth of N-polar AlN on 4H-SiC: Effect of substrate miscut on layer quality

    Science.gov (United States)

    Lemettinen, J.; Okumura, H.; Kim, I.; Kauppinen, C.; Palacios, T.; Suihkonen, S.

    2018-04-01

    We present the effect of miscut angle of SiC substrates on N-polar AlN growth. The N-polar AlN layers were grown on C-face 4H-SiC substrates with a miscut towards 〈 1 bar 1 0 0 〉 by metal-organic vapor phase epitaxy (MOVPE). The optimal V/III ratios for high-quality AlN growth on 1 ° and 4 ° miscut substrates were found to be 20,000 and 1000, respectively. MOVPE grown N-polar AlN layer without hexagonal hillocks or step bunching was achieved using a 4H-SiC substrate with an intentional miscut of 1 ° towards 〈 1 bar 1 0 0 〉 . The 200-nm-thick AlN layer exhibited X-ray rocking curve full width half maximums of 203 arcsec and 389 arcsec for (0 0 2) and (1 0 2) reflections, respectively. The root mean square roughness was 0.4 nm for a 2 μm × 2 μm atomic force microscope scan.

  11. Progress on n-type doping of AlGaN alloys on AlN single crystal substrates for UV optoelectronic applications

    Energy Technology Data Exchange (ETDEWEB)

    Collazo, Ramon; Rice, Anthony; Tweedie, James; Sitar, Zlatko [Department of Materials Science and Engineering, North Carolina State University, Raleigh, NC (United States); Mita, Seiji; Xie, Jinqiao; Dalmau, Rafael [HexaTech, Inc., Morrisville, NC (United States)

    2011-07-15

    As the building blocks of deep UV light emitting diode (LED) technology and high-power electronic devices, AlGaN alloys have attracted considerable attention. In this study, AlGaN films with varying compositions doped with Si were deposited on homoepitaxial AlN layers grown on AlN single crystal substrates. The room temperature resistivity of AlGaN alloys of different compositions grown on AlN and sapphire substrates with a constant Si doping level of 6x10{sup 18} cm{sup -3} was compared. AlGaN films grown on AlN substrates consistently exhibited a lower n-type resistivity than those grown on sapphire. An n-type resistivity of 0.1 {omega} cm was obtained for an AlGaN film with 80% Al content and a sheet resistance of 235 {omega}/sq. for an AlGaN film with 70% Al content. The carrier activation energy as a function of Al content in AlGaN for these n-type films was measured. For compositions below 80% Al, the activation energy was around 15 meV due to impurity potential screening. For higher Al compositions, the carrier concentration was limited by a high compensation ratio, except for AlN, which has activation energy of 250 meV. (copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  12. Sociality and the telencephalic distribution of corticotrophin-releasing factor, urocortin 3, and binding sites for CRF type 1 and type 2 receptors: A comparative study of eusocial naked mole-rats and solitary Cape mole-rats.

    Science.gov (United States)

    Coen, Clive W; Kalamatianos, Theodosis; Oosthuizen, Maria K; Poorun, Ravi; Faulkes, Christopher G; Bennett, Nigel C

    2015-11-01

    Various aspects of social behavior are influenced by the highly conserved corticotrophin-releasing factor (CRF) family of peptides and receptors in the mammalian telencephalon. This study has mapped and compared the telencephalic distribution of the CRF receptors, CRF1 and CRF2 , and two of their ligands, CRF and urocortin 3, respectively, in African mole-rat species with diametrically opposed social behavior. Naked mole-rats live in large eusocial colonies that are characterized by exceptional levels of social cohesion, tolerance, and cooperation in burrowing, foraging, defense, and alloparental care for the offspring of the single reproductive female. Cape mole-rats are solitary; they tolerate conspecifics only fleetingly during the breeding season. The telencephalic sites at which the level of CRF1 binding in naked mole-rats exceeds that in Cape mole-rats include the basolateral amygdaloid nucleus, hippocampal CA3 subfield, and dentate gyrus; in contrast, the level is greater in Cape mole-rats in the shell of the nucleus accumbens and medial habenular nucleus. For CRF2 binding, the sites with a greater level in naked mole-rats include the basolateral amygdaloid nucleus and dentate gyrus, but the septohippocampal nucleus, lateral septal nuclei, amygdalostriatal transition area, bed nucleus of the stria terminalis, and medial habenular nucleus display a greater level in Cape mole-rats. The results are discussed with reference to neuroanatomical and behavioral studies of various species, including monogamous and promiscuous voles. By analogy with findings in those species, we speculate that the abundance of CRF1 binding in the nucleus accumbens of Cape mole-rats reflects their lack of affiliative behavior. © 2015 Wiley Periodicals, Inc.

  13. Thermal conductivity of polycrystalline aluminum nitride (AlN ceramics Condutividade térmica de cerâmicas policristalinas de nitreto de alumínio (AlN

    Directory of Open Access Journals (Sweden)

    A. Franco Júnior

    2004-09-01

    Full Text Available In general, polycrystalline ceramics exhibit lower thermal conductivities than their associated single crystals. For instance, at 300K, the theoretical thermal conductivity of single crystal aluminum nitride (AlN is 319 W/m-K, whereas, the values measured for polycrystalline AlN ceramics range from 17 W/m-K to 285 W/m-K. This variation is not unusual for polycrystalline ceramics. The variability is strongly dependent upon the purity of the starting materials and the details of sintering process. The process is important since it influences the microstructure and thus influences the conduction mechanism. In this paper we present the causes of this variation and how it can be controlled.Em geral, cerâmicas policristalinas apresentam condutividade térmica mais baixa do que seus equivalentes monocristais. Por exemplo, a 300 K, a condutividade térmica teórica de monocristais de nitreto de alumínio (AlN é 319 W/m-K, enquanto que, os valores medidos variam desde 17 W/m-K a 285 W/m-K. Esta variação é comum em cerâmicas policristalinas. A variação é fortemente dependente do grau de pureza dos materiais precursores e detalhes dos processos de sinterização. O processo de sinterização é importante porque ele influencia a microestrutura e esta o mecanismo de condutividade. Neste artigo nós apresentamos as causas desta dependência e como ela pode ser controlada.

  14. Local lattice environment of indium in GaN, AlN, and InN; Lokale Gitterumgebung von Indium in GaN, AlN und InN

    Energy Technology Data Exchange (ETDEWEB)

    Penner, J.

    2007-12-20

    After an introduction to the physical properties of the nitrides, their preparation, and the state of studies on the implantation in the nitrides the experimental method (PAC) applied in this thesis and the data analysis are presented. The next chapter describes then the applied materials and the sample preparation. The following chapters contain the PAC measurements on the annealing behaviout of GaN, AlN, and InN after the implantation as well as dose- and temperature dependent PAC studies. Finally the most important results are summarized.

  15. Locomotor Activity and Body Temperature Patterns over a Temperature Gradient in the Highveld Mole-Rat (Cryptomys hottentotus pretoriae).

    Science.gov (United States)

    Haupt, Meghan; Bennett, Nigel C; Oosthuizen, Maria K

    2017-01-01

    African mole-rats are strictly subterranean mammals that live in extensive burrow systems. High humidity levels in the burrows prevent mole-rats from thermoregulating using evaporative cooling. However, the relatively stable environment of the burrows promotes moderate temperatures and small daily temperature fluctuations. Mole-rats therefore display a relatively wide range of thermoregulation abilities. Some species cannot maintain their body temperatures at a constant level, whereas others employ behavioural thermoregulation. Here we test the effect of ambient temperature on locomotor activity and body temperature, and the relationship between the two parameters, in the highveld mole-rat. We exposed mole-rats to a 12L:12D and a DD light cycle at ambient temperatures of 30°C, 25°C and 20°C while locomotor activity and body temperature were measured simultaneously. In addition, we investigated the endogenous rhythms of locomotor activity and body temperature at different ambient temperatures. Mole-rats displayed nocturnal activity at all three ambient temperatures and were most active at 20°C, but least active at 30°C. Body temperature was highest at 30°C and lowest at 20°C, and the daily cycle was highly correlated with locomotor activity. We show that the mole-rats have endogenous rhythms for both locomotor activity and body temperature. However, the endogenous body temperature rhythm appears to be less robust compared to the locomotor activity rhythm. Female mole-rats appear to be more sensitive to temperature changes than males, increased heterothermy is evident at lower ambient temperatures, whilst males show smaller variation in their body temperatures with changing ambient temperatures. Mole-rats may rely more heavily on behavioural thermoregulation as it is more energy efficient in an already challenging environment.

  16. Luminescence and Thermal Annealing of Sputtered Deposited - and Samarium-Doped Amorphous AlN Films

    Science.gov (United States)

    Maqbool, Muhammad

    Thin films of thulium- and samarium-doped AlN are deposited on silicon (111) substrates at 77 K by RF magnetron sputtering method. 200-400 nm thick films are grown at 100-200 watts RF power and 5-8 mTorr nitrogen, using a metal target of Al with Tm and Sm separately. X-rays diffraction results show that films are amorphous. Cathodoluminescence studies are performed at room temperature and two dominant peaks are observed in Tm at 467 nm from 1D2 → 3F4 transition and 480 nm from 1G4 to the ground state 3H6 transition. Other peaks in the visible region are obtained at 650 nm and 685 nm due to 1G4 → 3F4 and 1D2 → 3H4 transitions. Peaks in the ultraviolet and infrared region are also obtained at 371 nm and 802 nm as a result from 1D2 → 3H6 and 3H4 → 3H6 transition, respectively. Sm gives four peaks at 564 nm, 600 nm, 648 nm and 707 nm as a result of 4G5/2 → 6H5/2, 4G5/2 → 6H7/2, 4G5/2 → 6H9/2 and 4G5/2 → 6H11/2 transitions. Films are thermally annealed at 1200 K for half an hour in a nitrogen atmosphere. Thermal annealing enhances the intensity of luminescence.

  17. Twin Pregnancy with Hydatidiform Mole and Coexisting Fetus: Report of Three Cases and Review of Literature

    Directory of Open Access Journals (Sweden)

    Fariba Yarandi

    2009-03-01

    Full Text Available A twin pregnancy with a coexisting complete hydatidiform mole and a healthy fetus (CMCF is rare. Here we report three cases of CMCF with different clinical courses but similar outcome without a surviving neonate. Two women required uterine evacuation before 20 weeks of gestational age because of vaginal bleeding and medical complications and the other patient underwent termination of her pregnancy at 24 weeks of gestation due to severe pre-eclampsia. The pathologic diagnosis of complete hydatidiform mole was confirmed in each case and the chromosome complement was 46XX in two molar gestations and 46XY in one gestation. One of the three women required chemotherapy for treatment of low-risk gestational trophoblastic disease. The hCG level was normalized after 4 cycles and the patient was free of disease at 1 year follow-up. Review of the literature discussing the diagnostic tools, clinical features, management and outcome of pregnancies with CMCF are presented.

  18. Effects of ultraviolet radiation on mole rats kidney: A histopathologic and ultrastructural study

    Directory of Open Access Journals (Sweden)

    Hüseyin Türker

    2014-04-01

    Full Text Available The purpose of this study was to realize the ultrastructural effects of ultraviolet radiation on the kidney tissue cells of mole rats (Spalax leucodon. The mole rats of 180–200 g body weight were divided into the control and radiation-trial groups. The control group was not given any radiation. The other groups were irradiated with artificially produced UVC radiation for 14, 28 and 60 days. The kidney tissue samples were prepared at the end of experiments and analyzed by the light and electron microscope. Several effects were observed in the kidney tissues cells analyzed in accordance with the dose magnitude of radiation. These results clearly show the detrimental effects of UVC radiation on kidney tissue cells in exposure periods dependent on radiation dose and exposure time.

  19. Development of Field-Controlled Smart Optic Materials (ScN, AlN) with Rare Earth Dopants

    Science.gov (United States)

    Kim, Hyun-Jung; Park, Yeonjoon; King, Glen C.; Choi, Sang H.

    2012-01-01

    The purpose of this investigation is to develop the fundamental materials and fabrication technology for field-controlled spectrally active optics that are essential for industry, NASA, and DOD applications such as: membrane optics, filters for LIDARs, windows for sensors, telescopes, spectroscopes, cameras, flat-panel displays, etc. ScN and AlN thin films were fabricated on c-axis Sapphire (0001) or quartz substrate with the RF and DC magnetron sputtering. The crystal structure of AlN in fcc (rocksalt) and hcp (wurtzite) were controlled. Advanced electrical characterizations were performed, including I-V and Hall Effect Measurement. ScN film has a free carrier density of 5.8 x 10(exp 20)/per cubic centimeter and a conductivity of 1.1 x 10(exp 3) per centimeter. The background ntype conductivity of as-grown ScN has enough free electrons that can readily interact with the photons. The high density of free electrons and relatively low mobility indicate that these films contain a high level of shallow donors as well as deep levels. Also, the UV-Vis spectrum of ScN and AlN thin films with rare earth elements (Er or Ho) were measured at room temperature. Their optical band gaps were estimated to be about 2.33eV and 2.24eV, respectively, which are obviously smaller than that of undoped thin film ScN (2.4eV). The red-shifted absorption onset gives direct evidence for the decrease of band gap (Eg) and the energy broadening of valence band states are attributable to the doping. As the doped elements enter the ScN crystal lattices, the localized band edge states form at the doped sites with a reduction of Eg. Using a variable angle spectroscopic ellipsometer, the decrease in refractive index with applied field is observed with a smaller shift in absorption coefficient.

  20. Impacts of Thermal Atomic Layer-Deposited AlN Passivation Layer on GaN-on-Si High Electron Mobility Transistors.

    Science.gov (United States)

    Zhao, Sheng-Xun; Liu, Xiao-Yong; Zhang, Lin-Qing; Huang, Hong-Fan; Shi, Jin-Shan; Wang, Peng-Fei

    2016-12-01

    Thermal atomic layer deposition (ALD)-grown AlN passivation layer is applied on AlGaN/GaN-on-Si HEMT, and the impacts on drive current and leakage current are investigated. The thermal ALD-grown 30-nm amorphous AlN results in a suppressed off-state leakage; however, its drive current is unchanged. It was also observed by nano-beam diffraction method that thermal ALD-amorphous AlN layer barely enhanced the polarization. On the other hand, the plasma-enhanced chemical vapor deposition (PECVD)-deposited SiN layer enhanced the polarization and resulted in an improved drive current. The capacitance-voltage (C-V) measurement also indicates that thermal ALD passivation results in a better interface quality compared with the SiN passivation.

  1. Impacts of Thermal Atomic Layer-Deposited AlN Passivation Layer on GaN-on-Si High Electron Mobility Transistors

    Science.gov (United States)

    Zhao, Sheng-Xun; Liu, Xiao-Yong; Zhang, Lin-Qing; Huang, Hong-Fan; Shi, Jin-Shan; Wang, Peng-Fei

    2016-03-01

    Thermal atomic layer deposition (ALD)-grown AlN passivation layer is applied on AlGaN/GaN-on-Si HEMT, and the impacts on drive current and leakage current are investigated. The thermal ALD-grown 30-nm amorphous AlN results in a suppressed off-state leakage; however, its drive current is unchanged. It was also observed by nano-beam diffraction method that thermal ALD-amorphous AlN layer barely enhanced the polarization. On the other hand, the plasma-enhanced chemical vapor deposition (PECVD)-deposited SiN layer enhanced the polarization and resulted in an improved drive current. The capacitance-voltage (C-V) measurement also indicates that thermal ALD passivation results in a better interface quality compared with the SiN passivation.

  2. Digital dissection of the masticatory muscles of the naked mole-rat, Heterocephalus glaber (Mammalia, Rodentia

    Directory of Open Access Journals (Sweden)

    Philip G. Cox

    2014-06-01

    Full Text Available The naked mole-rat, Heterocephalus glaber, of the family Bathyergidae is a subterranean rodent that feeds on underground roots and tubers and digs extensive tunnel systems with its incisors. It is a highly unusual mammal with regard to its social structure, longevity, pain insensitivity and cancer resistance, all of which have made it the subject of a great deal of research in recent years. Yet, much of the basic anatomy of this species remains undocumented. In this paper, we describe the morphology of the jaw-closing musculature of the naked mole-rat, as revealed by contrast-enhanced micro-computed tomography. This technique uses an iodine stain to enable the imaging of soft tissues with microCT. The iodine-enhanced scans were used to create 3D reconstructions of the naked mole-rat masticatory muscles from which muscle masses were calculated. The jaw-closing musculature of Heterocephalus glaber is relatively very large compared to other rodents and is dominated by the superficial masseter, the deep masseter and the temporalis. The temporalis in particular is large for a rodent, covering the entirety of the braincase and much of the rear part of the orbit. The morphology of the masseter complex described here differs from two other published descriptions of bathyergid masticatory muscles, but is more similar to the arrangement seen in other rodent families. The zygomaticomandibularis (ZM muscle does not protrude through the infraorbital foramen on to the rostrum and thus the naked mole-rat should be considered protrogomorphous rather than hystricomorphous, and the morphology is consistent with secondarily lost hystricomorphy as has been previously suggested for Bathyergidae. Overall, the morphology of the masticatory musculature indicates a species with a high bite force and a wide gape–both important adaptations for a life dominated by digging with the incisors.

  3. Catalytic effect of Al and AlN interlayer on the growth and properties of containing carbon films

    International Nuclear Information System (INIS)

    Zhou, Bing; Liu, Zhubo; Tang, Bin; Rogachev, A.V.

    2015-01-01

    Highlights: • DLC and CN x bilayers with Al (AlN) interlayer were fabricated by cathode arc technique. • Complete diffusion of Al and C atoms occurs at the interface of Al/DLC (CN x ) bilayer. • Al/CN x bilayer presents a higher content of Csp 3 /Csp 2 bonds. • The hardness of Al/DLC bilayer decreases but increases for the other bilayers. • Morphology of the bilayers was explained by growth mechanism of DLC and surface state of substrate. - Abstract: Diamond-like carbon (DLC) and carbon nitride (CN x ) bilayer films with Al and AlN interlayer were fabricated by pulse cathode arc technique. The structure, composition, morphology and mechanical properties of the films were investigated by Raman, Auger electron spectroscopy (AES) and X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), Knoop sclerometer and surface profilometer. The results indicated that the complete diffusion between C and Al atoms occurs in the Al/DLC and Al/CN x bilayer. Al interlayer induces the increase of the size and ordering of Csp 2 clusters in the films but AlN interlayer increases the disordering degree of Csp 2 clusters. XPS results showed that a higher content of Csp 3 /Csp 2 bonds presents in the Al/CN x bilayer, and Al and AlN interlayer decreases the atomic ratio of N/C. AFM with phase contrast mode illustrated the morphologic characteristics of the bilayer films. All the bilayers show a nano-structural surface. The morphology changes of the bilayer were well explained by the surface state of the substrate and the growth mechanism of DLC films. The hardness of Al/DLC bilayer decreases but it increases for the other bilayers compared to the corresponding DLC (CN x ) monolayer. The internal stress of the bilayer is significantly lower than that of the monolayer except for the AlN/CN x bilayer. These studies could make the difference at the time of choosing a suitable functional film for certain application

  4. LUMINESCENCE AND THERMAL ANNEALING OF SPUTTERED DEPOSITED THULIUM- AND SAMARIUM-DOPED AMORPHOUS AlN FILMS

    OpenAIRE

    MUHAMMAD MAQBOOL

    2005-01-01

    Thin films of thulium- and samarium-doped AlN are deposited on silicon (111) substrates at 77 K by RF magnetron sputtering method. 200–400 nm thick films are grown at 100–200 watts RF power and 5–8 mTorr nitrogen, using a metal target of Al with Tm and Sm separately. X-rays diffraction results show that films are amorphous. Cathodoluminescence studies are performed at room temperature and two dominant peaks are observed in Tm at 467 nm from 1D2 → 3F4 transition and 480 nm from 1G4 to the grou...

  5. Energy harvesting based on piezoelectric AlN and AlScN thin films deposited by high rate sputtering

    Science.gov (United States)

    Frach, Peter; Barth, Stephan; Bartzsch, Hagen; Gloess, Daniel

    2017-05-01

    Aluminum nitride (AlN) is a piezoelectric material often used as thin film in SAW/BAW devices. Furthermore, there is an increasing interest in its use for energy harvesting applications. Despite it has a relatively low piezoelectric coefficient, it is a suitable choice for energy harvesting applications and due to its low dielectric constant and good mechanical properties. In addition, it is a lead-free material. The films were deposited by reactive pulsed magnetron sputtering using the Double Ring Magnetron DRM 400. This sputter source together with suitable powering and process control allows depositing piezoelectric AlN very homogeneously on 8" substrates with deposition rates of up to 200 nm/min. With the developed technology, film thicknesses of several ten microns are technically and economically feasible. Moreover, by adjusting process parameters accordingly, it is possible to tune properties, like film stress, to application specific requirements. Additionally, it is known that the doping of AlN with Scandium results in a significantly increased piezoelectric coefficient. The influence of process parameters and Sc concentration on film properties were determined by piezometer, pulse echo, SEM, XRD, EDS and nanoindentation measurements. Energy harvesting measurements were done using an electromechanical shaker system for the excitation of defined vibrations and a laservibrometer for determination of the displacement of the samples. The generated power was measured as function of electric load at resonance. An rms power of up to 140μW using AlN films and of 350μW using AlScN films was generated on Si test pieces of 8x80mm2. Furthermore, energy harvesting measurements using manually bended steel strips of 75x25mm2 coated with AlScN were carried out as well. When using only a single actuation, energy of up to 8μJ could be measured. By letting the system vibrate freely, the damped vibration at resonance 50Hz resulted in a measured energy of 420μJ.

  6. High energy ion irradiated III-N semiconductors (AlN, GaN, InN): study of point defect and extended defect creation

    International Nuclear Information System (INIS)

    Sall, Mamour

    2013-01-01

    Nitride semiconductors III N (AlN, GaN, InN) have interesting properties for micro-and opto-electronic applications. In use, they may be subjected to different types of radiation in a wide range of energy. In AlN, initially considered insensitive to electronic excitations (Se), we have demonstrated a novel type of synergy between Se and nuclear collisions (Sn) for the creation of defects absorbing at 4.7 eV. In addition, another effect of Se is highlighted in AlN: climb of screw dislocations under the influence of Se, at high fluence. In GaN, two mechanisms can explain the creation of defects absorbing at 2.8 eV: a synergy between Se and Sn, or a creation only due to Sn but with a strong effect of the size of displacement cascades. The study, by TEM, of the effects of Se in the three materials, exhibits behaviors highly dependent on the material while they all belong to the same family with the same atomic structure. Under monoatomic ion irradiations (velocity between 0.4 and 5 MeV/u), while discontinuous tracks are observed in GaN and InN, no track is observed in AlN with the highest electronic stopping power (33 keV/nm). Only fullerene clusters produce tracks in AlN. The inelastic thermal spike model was used to calculate the energies required to produce track in AlN, GaN and InN, they are 4.2 eV/atom, 1.5 eV/atom and 0.8 eV/atom, respectively. This sensitivity difference according to Se, also occurs at high fluence. (author)

  7. Cancer resistance in the blind mole rat is mediated by concerted necrotic cell death mechanism

    Science.gov (United States)

    Gorbunova, Vera; Hine, Christopher; Tian, Xiao; Ablaeva, Julia; Gudkov, Andrei V.; Nevo, Eviatar; Seluanov, Andrei

    2012-01-01

    Blind mole rats Spalax (BMR) are small subterranean rodents common in the Middle East. BMR is distinguished by its adaptations to life underground, remarkable longevity (with a maximum documented lifespan of 21 y), and resistance to cancer. Spontaneous tumors have never been observed in spalacids. To understand the mechanisms responsible for this resistance, we examined the growth of BMR fibroblasts in vitro of the species Spalax judaei and Spalax golani. BMR cells proliferated actively for 7–20 population doublings, after which the cells began secreting IFN-β, and the cultures underwent massive necrotic cell death within 3 d. The necrotic cell death phenomenon was independent of culture conditions or telomere shortening. Interestingly, this cell behavior was distinct from that observed in another long-lived and cancer-resistant African mole rat, Heterocephalus glaber, the naked mole rat in which cells display hypersensitivity to contact inhibition. Sequestration of p53 and Rb proteins using SV40 large T antigen completely rescued necrotic cell death. Our results suggest that cancer resistance of BMR is conferred by massive necrotic response to overproliferation mediated by p53 and Rb pathways, and triggered by the release of IFN-β. Thus, we have identified a unique mechanism that contributes to cancer resistance of this subterranean mammal extremely adapted to life underground. PMID:23129611

  8. Sex, social status, and CRF receptor densities in naked mole-rats.

    Science.gov (United States)

    Beery, Annaliese K; Bicks, Lucy; Mooney, Skyler J; Goodwin, Nastacia L; Holmes, Melissa M

    2016-02-01

    Naked mole-rats (Heterocephalus glaber) live in groups that are notable for their large size and caste structure, with breeding monopolized by a single female and a small number of males. Recent studies have demonstrated substantial differences between the brains of breeders and subordinates induced by changes in social standing. Corticotropin-releasing factor (CRF) receptors-which bind the hormone CRF as well as related peptides-are important regulators of stress and anxiety, and are emerging as factors affecting social behavior. We conducted autoradiographic analyses of CRF1 and CRF2 receptor binding densities in female and male naked mole-rats varying in breeding status. Both globally and in specific brain regions, CRF1 receptor densities varied with breeding status. CRF1 receptor densities were higher in subordinates across brain regions, and particularly in the piriform cortex and cortical amygdala. Sex differences were present in CRF2 receptor binding densities, as is the case in multiple vole species. CRF2 receptor densities were higher in females, both globally and in the cortical amygdala and lateral amygdalar nucleus. These results provide novel insights into the neurobiology of social hierarchy in naked mole-rats, and add to a growing body of work that links changes in the CRF system with social behavior. © 2015 Wiley Periodicals, Inc.

  9. Cutaneous and periodontal inputs to the cerebellum of the naked mole-rat (Heterocephalus glaber).

    Science.gov (United States)

    Sarko, Diana K; Leitch, Duncan B; Catania, Kenneth C

    2013-01-01

    The naked mole-rat (Heterocephalus glaber) is a small fossorial rodent with specialized dentition that is reflected by the large cortical area dedicated to representation of the prominent incisors. Due to naked mole-rats' behavioral reliance on the incisors for digging and for manipulating objects, as well as their ability to move the lower incisors independently, we hypothesized that expanded somatosensory representations of the incisors would be present within the cerebellum in order to accommodate a greater degree of proprioceptive, cutaneous, and periodontal input. Multiunit electrophysiological recordings targeting the ansiform lobule were used to investigate tactile inputs from receptive fields on the entire body with a focus on the incisors. Similar to other rodents, a fractured somatotopy appeared to be present with discrete representations of the same receptive fields repeated within each folium of the cerebellum. These findings confirm the presence of somatosensory inputs to a large area of the naked mole-rat cerebellum with particularly extensive representations of the lower incisors and mystacial vibrissae. We speculate that these extensive inputs facilitate processing of tactile cues as part of a sensorimotor integration network that optimizes how sensory stimuli are acquired through active exploration and in turn adjusts motor outputs (such as independent movement of the lower incisors). These results highlight the diverse sensory specializations and corresponding brain organizational schemes that have evolved in different mammals to facilitate exploration of and interaction with their environment.

  10. Cutaneous and periodontal inputs to the cerebellum of the naked mole-rat (Heterocephalus glaber

    Directory of Open Access Journals (Sweden)

    Diana K Sarko

    2013-11-01

    Full Text Available The naked mole-rat (Heterocephalus glaber is a small fossorial rodent with specialized dentition that is reflected by the large cortical area dedicated to representation of the prominent incisors. Due to naked mole-rats’ behavioral reliance on the incisors for digging and for manipulating objects, as well as their ability to move the lower incisors independently, we hypothesized that expanded somatosensory representations of the incisors would be present within the cerebellum in order to accommodate a greater degree of proprioceptive, cutaneous, and periodontal input. Multiunit electrophysiological recordings targeting the ansiform lobule were used to investigate tactile inputs from receptive fields on the entire body with a focus on the incisors. Similar to other rodents, a fractured somatotopy appeared to be present with discrete representations of the same receptive fields repeated within each folium of the cerebellum. These findings confirm the presence of somatosensory inputs to a large area of the naked mole-rat cerebellum with particularly extensive representations of the lower incisors and mystacial vibrissae. We speculate that these extensive inputs facilitate processing of tactile cues as part of a sensorimotor integration network that optimizes how sensory stimuli are acquired through active exploration and in turn adjusts motor outputs (such as independent movement of the lower incisors. These results highlight the diverse sensory specializations and corresponding brain organizational schemes that have evolved in different mammals to facilitate exploration of and interaction with their environment.

  11. Naked mole-rat mortality rates defy Gompertzian laws by not increasing with age

    Science.gov (United States)

    Ruby, J Graham; Smith, Megan

    2018-01-01

    The longest-lived rodent, the naked mole-rat (Heterocephalus glaber), has a reported maximum lifespan of >30 years and exhibits delayed and/or attenuated age-associated physiological declines. We questioned whether these mouse-sized, eusocial rodents conform to Gompertzian mortality laws by experiencing an exponentially increasing risk of death as they get older. We compiled and analyzed a large compendium of historical naked mole-rat lifespan data with >3000 data points. Kaplan-Meier analyses revealed a substantial portion of the population to have survived at 30 years of age. Moreover, unlike all other mammals studied to date, and regardless of sex or breeding-status, the age-specific hazard of mortality did not increase with age, even at ages 25-fold past their time to reproductive maturity. This absence of hazard increase with age, in defiance of Gompertz’s law, uniquely identifies the naked mole-rat as a non-aging mammal, confirming its status as an exceptional model for biogerontology. PMID:29364116

  12. Facultative Parasitism by the Bivalve Kurtiella pedroana in the Mole Crab Emerita analoga.

    Science.gov (United States)

    Bhaduri, R N; Valentich-Scott, P; Hilgers, M S; Singh, R; Hickman, M E; Lafferty, K D

    2017-12-01

    Evolutionary transitions to parasitism are rare. In this study, we documented a potential step toward parasitism in the commensal clam Kurtiella pedroana (Bivalvia: Galeommatoidea). Galeommatoideans are known commensals of various invertebrates, including crustaceans. Emerita analoga (Decapoda: Hippidae) is an abundant intertidal mole crab inhabiting Pacific coast beaches in North and South America. Mole crabs collected from Monterey Bay, California, were measured and examined externally and internally for associated molluscs. Out of the 520 mole crabs, 37 large female individuals harbored 49 clams (prevalence of 7.11% and mean intensity of 1.3). Forty-one ectocommensal clams were attached by their byssal threads to the inside of the gill chambers or to the lateroventral surfaces. However, our key finding was 8 clams that lacked byssal threads and were living in the hemocoel of 6 crabs. These internal clams were smaller than the ectocommensals. Because these internal clams lacked access to their normal food, we hypothesize they might have fed on hemolymph as would a parasite. Clam larvae have no obvious exit from the hemocoel, implying that endoparasitism is a dead-end for K. pedroana. Regardless, facultative parasitism in a free-living or an ectocommensal is uncommon and suggests a pathway to parasitism.

  13. Analyzing difficulties with mole-concept tasks by using familiar analog tasks

    Science.gov (United States)

    Gabel, Dorothy; Sherwood, Robert D.

    This study was conducted to determine which skills and concepts students have that are prerequisites for solving moles problems through the use of analog tasks. Two analogous tests with four forms of each were prepared that corresponded to a conventional moles test. The analogs used were oranges and granules of sugar. Slight variations between test items on various forms permitted comparisons that would indicate specific conceptual and mathematical difficulties that students might have in solving moles problems. Different forms of the two tests were randomly assigned to 332 high school chemistry students of five teachers in four schools in central Indiana. Comparisons of total test score, subtest scores, and the number of students answering an item correctly using appropriate t-test and chi square tests resulted in the following conclusions: (1) the size of the object makes no difference in the problem difficulty; (2) students understand the concepts of mass, volume, and particles equally well; (3) problems requiring two steps are harder than those requiring one step; (4) problems involving scientific notation are more difficult than those that do not; (5) problems involving the multiplication concept are easier than those involving the division concept; (6) problems involving the collective word bag are easier to solve than those using the word billion; (7) the use of the word a(n) makes the problem more difficult than using the number 1.

  14. Modeling of Lithium Niobate (LiNbO3) and Aluminum Nitride (AlN) Nanowires Using Comsol Multiphysics Software: The Case of Pressure Sensor

    Science.gov (United States)

    Ahmad, A. A.; Alsaad, A.; Al-Bataineh, Q. M.; Al-Naafa, M. A.

    2018-02-01

    In this study, Lithium niobate (LiNbO3) and Aluminum nitride (AlN) nanostructures were designed and investigated using the COMSOL Multiphysics software for pressure sensing applications. The Finite Element Method (FEM) was used for solving the differential equations with various parameters such as size, length, force, etc. The variation of the total maximum displacement as a function of applied force for various NWs lengths and the variation of the voltage as a function of applied force were plotted and discussed. AlN nanowires exhibit a better piezoelectric response than LiNbO3 nanowires do.

  15. On a reduction in cracking upon the growth of AlN on Si substrates by hydride vapor-phase epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Sharofidinov, Sh. Sh., E-mail: shukrillo71@mail.ru; Nikolaev, V. I.; Smirnov, A. N.; Chikiryaka, A. V.; Nikitina, I. P. [Russian Academy of Sciences, Ioffe Physical–Technical Institute (Russian Federation); Odnoblyudov, M. A. [St. Petersburg State Polytechnic University (Russian Federation); Bugrov, V. E. [St. Petersburg National Research University of Information Technologies, Mechanics and Optics (Russian Federation); Romanov, A. E. [Russian Academy of Sciences, Ioffe Physical–Technical Institute (Russian Federation)

    2016-04-15

    The main problem of the epitaxial growth of thick AlN layers on a Si substrate consists in the formation of cracks, which complicates the application of structures of this kind in the fabrication of semiconductor devices. The possibility of obtaining crack-free AlN layers with a thickness exceeding 1 μm and a mirror- smooth surface by hydride vapor-phase epitaxy is demonstrated. The properties of the layers are studied by X-diffraction analysis, optical and scanning electron microscopy, and Raman spectroscopy.

  16. Hydatidiform mole

    Science.gov (United States)

    ... avoid another pregnancy and to use a reliable contraceptive for 6 to 12 months after treatment for ... Hockberger RS, Walls RM, et al, eds. Rosen's Emergency Medicine . 8th ed. Philadelphia, PA: Elsevier Saunders; 2014: ...

  17. Moles (Nevi)

    Science.gov (United States)

    ... AAD Contact us Support AAD Media AAD store Advertise Employment Website feedback "); document.write(""); document.write(" Cart "); } ... Registration General information Housing & travel Education Exhibit hall Mobile app 2019 Annual Meeting Derm Exam Prep Course ...

  18. Investigation of the presence and antinociceptive function of muscarinic acetylcholine receptors in the African naked mole-rat (Heterocephalus glaber)

    DEFF Research Database (Denmark)

    Jørgensen, Kristine B.; Krogh-Jensen, Karen; Pickering, Darryl S

    2016-01-01

    The present study investigated the cholinergic system in the African naked mole-rat (Heterocephalus glaber) with focus on the muscarinic acetylcholine receptor subtypes M1 and M4. The protein sequences for the subtypes m 1–5 of the naked mole-rat were compared to that of the house mouse (Mus...... musculus) using basic local alignment search tool (BLAST). The presence and function of M1 and M4 was investigated in vivo, using the formalin test with the muscarinic receptor agonists xanomeline and VU0152100. Spinal cord tissue from the naked mole-rat was used for receptor saturation binding studies...... with [3H]-N-methylscopolamine. The BLAST test revealed 95 % protein sequence homology showing the naked mole-rat to have the genetic potential to express all five muscarinic acetylcholine receptor subtypes. A significant reduction in pain behavior was demonstrated after administration of 8.4 mg...

  19. Reproductive suppression and the seasonality of reproduction in the social Natal mole-rat (Cryptomys hottentotus natalensis).

    Science.gov (United States)

    Oosthuizen, M K; Bennett, N C; Lutermann, H; Coen, C W

    2008-01-01

    Natal mole-rats are social subterranean rodents which exhibit a reproductive division of labour. Reproduction is confined to a single breeding female and one or more males; the remainder of the colony members is reproductively suppressed by the presence of the breeding animals. Apart from the discovery that female Natal mole-rats are induced ovulators, little is known about the reproductive biology of this species. Natal mole-rats are closely related to common and highveld mole-rats, both of which are induced ovulators and seasonal breeders. We therefore postulated that reproduction in Natal mole-rats is seasonally regulated. However, the results indicate that dominant Natal mole-rats are able to reproduce in the winter as well as in the summer. Furthermore, the increment in plasma LH in response to GnRH does not show marked seasonal differences in reproductive or non-reproductive mole-rats of either sex. Nevertheless, in all reproductive categories the level of plasma LH is significantly higher in the winter than in the summer. Seasonality in plasma LH levels dissociated from seasonality in breeding seems paradoxical. Further investigations will be required to elucidate this finding. We also investigated the processes underlying socially regulated reproduction in this species by determining basal and GnRH-evoked plasma LH in reproductive and non-reproductive animals of each sex in both seasons. The results failed to identify neuroendocrine differences consistent with an inhibited reproductive state in subordinates of either sex. Thus, the present findings suggest that behavioural interactions and/or inbreeding avoidance are the principal factors underlying suppression of reproduction in subordinate Natal mole-rats.

  20. Community structure variability of Uropodina mites (Acari: Mesostigmata) in nests of the common mole, Talpa europaea, in Central Europe

    OpenAIRE

    Napiera?a, Agnieszka; M?dra, Anna; Leszczy?ska-Deja, Kornelia; Gwiazdowicz, Dariusz J.; Go?dyn, Bart?omiej; B?oszyk, Jerzy

    2016-01-01

    Underground nests of Talpa europaea, known as the common mole, are very specific microhabitats, which are also quite often inhabited by various groups of arthropods. Mites from the suborder Uropodina (Acari: Mesostigmata) are only one of them. One could expect that mole nests that are closely located are inhabited by communities of arthropods with similar species composition and structure. However, results of empirical studies clearly show that even nests which are close to each other can be ...

  1. Thermal expansions in wurtzite AlN, GaN, and InN: First-principle phonon calculations

    Science.gov (United States)

    Xu, Li-Chun; Wang, Ru-Zhi; Yang, Xiaodong; Yan, Hui

    2011-08-01

    Using the first-principle phonon calculations under the quasiharmonic approximation, thermal expansions in III-nitrides with wurtzite AlN, GaN, and InN are reported. The results showed that it is different for each thermal expansion of three III-nitrides at low temperatures, which is consistent with their Grüneisen parameters as the function of temperature. Below 50 K, negative thermal expansions occur in InN, while GaN and AlN follow the rule of positive thermal expansion. To seek the origin of positive/negative thermal expansion distinction, the mode Grüneisen parameters and the phonon spectra are investigated. They indicate that different low-frequency phonon vibration modes correspond to the change of thermal expansions. Below 5 THz, the significant weighted negative values of mode Grüneisen parameters, caused by the weakening of mixing-mode constituted with two transverse acoustic (TA) modes and a small overlapped part of optical modes, directly lead to the negative thermal expansion at low temperatures.

  2. Effect of Ga2O3 addition on the properties of Y2O3-doped AlN ceramics

    Directory of Open Access Journals (Sweden)

    Shin H.

    2015-01-01

    Full Text Available Effect Ga2O3 addition on the densification and properties of Y2O3-doped AlN ceramics was investigated under the constraint of total sintering additives (Y2O3 and Ga2O3 of 4.5 wt%. Ga was detected in the AlN grain as well as the grain boundary phases. YAlO3 and Y4Al2O9 were observed as the secondary crystalline phases in all of the investigated compositions. As the substitution of Ga2O3 for Y2O3 increased, the quantity of the Y4Al2O9 phase decreased while that of YAlO3 was more or less similar. Neither additional secondary phases was identified, nor was the sinterability inhibited by the Ga2O3 addition; the linear shrinkage and apparent density were above 20 percent and 3.34-3.37 g/cm3, respectively. However, the optical reflectance and the elastic modulus generally decreased whereas the Poisson ratio increased significantly. The dielectric constant and the loss tangent of 4.0Y2O3-0.5Ga2O3-95.5Y2O3 at the resonant frequency of 8.22 GHz were 8.63 and 0.003, respectively.

  3. Frequency response improvement of a two-port surface acoustic wave device based on epitaxial AlN thin film

    Science.gov (United States)

    Gao, Junning; Hao, Zhibiao; Luo, Yi; Li, Guoqiang

    2018-01-01

    This paper presents an exploration on improving the frequency response of the symmetrical two-port AlN surface acoustic wave (SAW) device, using epitaxial AlN thin film on (0001) sapphire as the piezoelectric substrate. The devices were fabricated by lift-off processes with Ti/Al composite electrodes as interleaved digital transducers (IDT). The impact of DL and the number of the IDT finger pairs on the frequency response was carefully investigated. The overall properties of the device are found to be greatly improved with DL elongation, indicated by the reduced pass band ripple and increased stop band rejection ratio. The rejection increases by 8.3 dB when DL elongates from 15.5λ to 55.5λ and 4.4 dB further accompanying another 50λ elongation. This is because larger DL repels the stray acoustic energy out of the propagation path and provides a cleaner traveling channel for functional SAW, and at the same time restrains electromagnetic feedthrough. It is also found that proper addition of the IDT finger pairs is beneficial for the device response, indicated by the ripple reduction and the insertion loss drop.

  4. Structural and electrical properties of AlN layers grown on silicon by reactive RF magnetron sputtering

    Energy Technology Data Exchange (ETDEWEB)

    Bazlov, N., E-mail: n.bazlov@spbu.ru; Pilipenko, N., E-mail: nelly.pilipenko@gmail.com; Vyvenko, O.; Petrov, Yu.; Mikhailovskii, V.; Ubyivovk, E. [St. Petersburg State University, Ulyanovskaya 1, Petrodvorets, St.Petersburg (Russian Federation); Kotina, I. [St. Petersburg Nuclear Physics Institute, Gatchina, Leningradskii oblast, 188300 (Russian Federation); Zharinov, V. [INPAC—Institute for Nanoscale Physics and Chemistry, Department of Physics and Astronomy, KU Leuven, Celestijnenlaan 200D, B-3001 Leuven (Belgium)

    2016-06-17

    AlN films of different thicknesses were deposited on n-Si (100) substrates by reactive radio frequency (rf) magnetron sputtering. Dependences of structure and electrical properties on thickness of deposited films were researched. The structures of the films were analyzed with scanning electron microscopy (SEM) and with transmitting electron microscopy (TEM). Electrical properties of the films were investigated on Au-AlN-(n-Si) structures by means of current-voltage (I-V), capacitance-voltage (C-V) and deep level transient spectroscopy (DLTS) techniques. Electron microscopy investigations had shown that structure and chemical composition of the films were thickness stratified. Near silicon surface layer was amorphous aluminum oxide one contained traps of positive charges with concentration of about 4 × 10{sup 18} cm{sup −3}. Upper layers were nanocrystalline ones consisted of both wurzite AlN and cubic AlON nanocrystals. They contained traps both positive and negative charges which were situated within 30 nm distance from silicon surface. Surface densities of these traps were about 10{sup 12} cm{sup −2}. Electron traps with activation energies of (0.2 ÷ 0.4) eV and densities of about 10{sup 10} cm{sup −2} were revealed on interface between aluminum oxide layer and silicon substrate. Their densities varied weakly with the film thickness.

  5. Influence of the crystal orientation on the electrical properties of AlN thin films on LTCC substrates

    Energy Technology Data Exchange (ETDEWEB)

    Bittner, A., E-mail: achim.bittner@tuwien.ac.at [Micromechanics, Microfluidics/Microactuators, Faculty of Natural Sciences and Technology II, Saarland University, D-66123 Saarbruecken (Germany); Ababneh, A.; Seidel, H. [Micromechanics, Microfluidics/Microactuators, Faculty of Natural Sciences and Technology II, Saarland University, D-66123 Saarbruecken (Germany); Schmid, U. [Department for Microsystems Technology, Institute of Sensor and Actuator Systems, Vienna University of Technology, Floragasse 7, A-1040 Vienna (Austria)

    2010-11-15

    In this study, the influence of the crystal orientation on the electrical properties of sputter deposited aluminium nitride (AlN) thin films on low temperature co-fired ceramics (LTCC) substrates is investigated. The degree of c-axis orientation can be tailored by the deposition conditions such as plasma power, gas pressure and gas composition in the deposition chamber. Due to the large surface roughness of LTCC substrates (R{sub a} = {approx}0.4 {mu}m) the quality of thin films is lower compared to silicon. Between areas of columnar grains arranged perpendicular to the LTCC surface, defects like voids are generated due to the wavy surface characteristics. The impact of crystal orientation and temperature up to 400 deg. C on the electrical performance is evaluated, as these layers are targeted as potential candidates for dielectric heat spreaders on multilayered ceramic substrates for high frequency applications. These AlN thin films having a good c-axis orientation exhibit lower leakage current levels over the complete temperature range compared to those with a poor alignment with respect to this crystallographic plane. The leakage current behaviour, however, is dominated according to the Pool-Frenkel electron emission independent of the degree of c-axis orientation.

  6. Characterization of a smartphone size haptic rendering system based on thin-film AlN actuators on glass substrates

    International Nuclear Information System (INIS)

    Bernard, F; Basrour, S; Casset, F; Danel, J S; Chappaz, C

    2016-01-01

    This paper presents for the first time the characterization of a smartphone-size haptic rendering system based on the friction modulation effect. According to previous work and finite element modeling, the homogeneous flexural modes are needed to get the haptic feedback effect. The device studied consists of a thin film AlN transducers deposited on an 110  ×  65 mm 2 glass substrate. The transducer’s localization on the glass plate allows a transparent central area of 90  ×  49 mm 2 . Electrical and mechanical parameters of the system are extracted from measurement. From this extraction, the electrical impedance matching reduced the applied voltage to 17.5 V AC and the power consumption to 1.53 W at the resonance frequency of the vibrating system to reach the haptic rendering specification. Transient characterizations of the actuation highlight a delay under the dynamic tactile detection. The characterization of the AlN transducers used as sensors, including the noise rejection, the delay or the output charge amplitude allows detections with high accuracy of any variation due to external influences. Those specifications are the first step to a low-power-consumption feedback-looped system. (paper)

  7. The Variations of Thermal Contact Resistance and Heat Transfer Rate of the AlN Film Compositing with PCM

    Directory of Open Access Journals (Sweden)

    Huann-Ming Chou

    2015-01-01

    Full Text Available The electrical industries have been fast developing over the past decades. Moreover, the trend of microelements and packed division multiplex is obviously for the electrical industry. Hence, the high heat dissipative and the electrical insulating device have been popular and necessary. The thermal conduct coefficient of aluminum nitride (i.e., AlN is many times larger than the other materials. Moreover, the green technology of composite with phase change materials (i.e., PCMs is worked as a constant temperature cooler. Therefore, PCMs have been used frequently for saving energy and the green environment. Based on the above statements, it does show great potential in heat dissipative for the AlN film compositing with PCM. Therefore, this paper is focused on the research of thermal contact resistance and heat transfer between the AlN/PCM pairs. According to the experimental results, the heat transfer decreases and the thermal contact resistance increases under the melting process of PCM. However, the suitable parameters such as contact pressures can be used to improve the above defects.

  8. The growth of Sea-urchin-like AlN nanostructures by modified CVD and their Field Emission properties

    Science.gov (United States)

    Guo, Lu`an; Chen, Guangde; Zhu, Youzhang; Duan, Xiangyang; Ye, Honggang

    2015-09-01

    AlN complex nanostructures were fabricated by using chemical vapor deposition (CVD) method which was carried out at a low moderate temperature ( 750 °C) and without any catalyst. Field emission scanning electron microscopy (FESEM), X-Ray diffraction, transmission electron microscopy (TEM), and Raman scattering spectrum were used to characterize the microstructures and morphologies of the products. The FESEM results of samples exhibit unordered nanoneedle lawn-like interspersed by the Sea-urchin-like morphology, in which many needle-like nanostructures with the length of 500 nm grow radially from a central nucleus. The results of the X-ray, TEM and Raman scattering spectrum indicate that the samples have a preferential growth along the [0001] direction good quality AlN nanostructure. The field emission device testing shows that the Sea-urchin-like nanostructure has a very low turn-on electric field of 3.6 V/μm (0.01 mA/cm2) and a very high field enhancement factor β (2.1×103) at room temperature. It suggests that it can be used for field emission displays and vacuum microelectronic devices.

  9. Fractional Vector Calculus and Fractional Special Function

    OpenAIRE

    Li, Ming-Fan; Ren, Ji-Rong; Zhu, Tao

    2010-01-01

    Fractional vector calculus is discussed in the spherical coordinate framework. A variation of the Legendre equation and fractional Bessel equation are solved by series expansion and numerically. Finally, we generalize the hypergeometric functions.

  10. Efficacy of NETDC (New England Trophoblastic Disease Center prognostic index score to predict gestational trophoblastic tumor from hydatidiform mole

    Directory of Open Access Journals (Sweden)

    Khrismawan Khrismawan

    2004-03-01

    Full Text Available A prospective longitudinal analytic study assessing the efficacy of NETDC (New England Trophoblastic Disease Center prognostic index score in predicting malignancy after hydatidiform mole had been performed. Of the parameter evaluated; age of patients, type of hydatidiform mole, uterine enlargement, serum hCG level, lutein cyst, and presence of complicating factors were significant risk factors for malignancy after hydatidiform mole were evacuated (p<0.032. The study were done on 50 women diagnosed with hydatidiform mole with 1 year observation (January 2001-December 2002 at the Department of Obstetrics and Gynecology, Mohammad Hoesin Hospital, Palembang. The results showed that the NETDC prognostic index score predicted malignancy in 50% of high risk group and 10% in low risk group (p<0.05. This showed a higher number than that found by the WHO (19%-30%. The risk for incidence of  malignancy after hydatidiform mole in the high risk group is 9.0 times higher compared to that of the low risk group (CI: 1.769-45.786. (Med J Indones 2004; 13: 40-6 Keywords: New England Trophoblastic Disease Center (NETDC, gestational trophoblastic tumor, hydatidiform mole, high and low risk

  11. Investigation of the presence and antinociceptive function of muscarinic acetylcholine receptors in the African naked mole-rat (Heterocephalus glaber).

    Science.gov (United States)

    Jørgensen, Kristine B; Krogh-Jensen, Karen; Pickering, Darryl S; Kanui, Titus I; Abelson, Klas S P

    2016-01-01

    The present study investigated the cholinergic system in the African naked mole-rat (Heterocephalus glaber) with focus on the muscarinic acetylcholine receptor subtypes M1 and M4. The protein sequences for the subtypes m 1-5 of the naked mole-rat were compared to that of the house mouse (Mus musculus) using basic local alignment search tool (BLAST). The presence and function of M1 and M4 was investigated in vivo, using the formalin test with the muscarinic receptor agonists xanomeline and VU0152100. Spinal cord tissue from the naked mole-rat was used for receptor saturation binding studies with [(3)H]-N-methylscopolamine. The BLAST test revealed 95 % protein sequence homology showing the naked mole-rat to have the genetic potential to express all five muscarinic acetylcholine receptor subtypes. A significant reduction in pain behavior was demonstrated after administration of 8.4 mg/kg in the formalin test. Administration of 50 mg/kg VU0152100 resulted in a non-significant tendency towards antinociception. The antinociceptive effects were reversed by the muscarinic acetylcholine receptor antagonist atropine. Binding studies indicated presence of muscarinic acetylcholine receptors with a radioligand affinity comparable to that reported in mice. In conclusion, muscarinic acetylcholine receptor subtypes are present in the naked mole-rat and contribute to antinociception in the naked mole-rat.

  12. Hypofunctional TrkA Accounts for the Absence of Pain Sensitization in the African Naked Mole-Rat

    Directory of Open Access Journals (Sweden)

    Damir Omerbašić

    2016-10-01

    Full Text Available The naked mole-rat is a subterranean rodent lacking several pain behaviors found in humans, rats, and mice. For example, nerve growth factor (NGF, an important mediator of pain sensitization, fails to produce thermal hyperalgesia in naked mole-rats. The sensitization of capsaicin-sensitive TRPV1 ion channels is necessary for NGF-induced hyperalgesia, but naked mole-rats have fully functional TRPV1 channels. We show that exposing isolated naked mole-rat nociceptors to NGF does not sensitize TRPV1. However, the naked mole-rat NGF receptor TrkA displays a reduced ability to engage signal transduction pathways that sensitize TRPV1. Between one- and three-amino-acid substitutions in the kinase domain of the naked mole-rat TrkA are sufficient to render the receptor hypofunctional, and this is associated with the absence of heat hyperalgesia. Our data suggest that evolution has selected for a TrkA variant that abolishes a robust nociceptive behavior in this species but is still compatible with species fitness.

  13. Hypofunctional TrkA Accounts for the Absence of Pain Sensitization in the African Naked Mole-Rat.

    Science.gov (United States)

    Omerbašić, Damir; Smith, Ewan St J; Moroni, Mirko; Homfeld, Johanna; Eigenbrod, Ole; Bennett, Nigel C; Reznick, Jane; Faulkes, Chris G; Selbach, Matthias; Lewin, Gary R

    2016-10-11

    The naked mole-rat is a subterranean rodent lacking several pain behaviors found in humans, rats, and mice. For example, nerve growth factor (NGF), an important mediator of pain sensitization, fails to produce thermal hyperalgesia in naked mole-rats. The sensitization of capsaicin-sensitive TRPV1 ion channels is necessary for NGF-induced hyperalgesia, but naked mole-rats have fully functional TRPV1 channels. We show that exposing isolated naked mole-rat nociceptors to NGF does not sensitize TRPV1. However, the naked mole-rat NGF receptor TrkA displays a reduced ability to engage signal transduction pathways that sensitize TRPV1. Between one- and three-amino-acid substitutions in the kinase domain of the naked mole-rat TrkA are sufficient to render the receptor hypofunctional, and this is associated with the absence of heat hyperalgesia. Our data suggest that evolution has selected for a TrkA variant that abolishes a robust nociceptive behavior in this species but is still compatible with species fitness. Copyright © 2016 The Authors. Published by Elsevier Inc. All rights reserved.

  14. Epitaxial AlN layers on sapphire and diamond; Epitaktische AlN-Schichten auf Saphir und Diamant

    Energy Technology Data Exchange (ETDEWEB)

    Hermann, Martin

    2009-04-27

    In this work, epitaxial AlN layers deposited by molecular beam epitaxy on sapphire and diamond substrates were investigated. Starting from this AlN, the dopant silicon was added. The influence of the silicon doping on the structural properties of the host AlN crystal was investigated using high resolution X-ray diffraction. Once the silicon concentration exceeds 1 x 10{sup 19} cm{sup -3}, a significant change of the AlN:Si crystal can be observed: increasing the silicon concentration up to 5 x 10{sup 20} cm{sup -3} results in a decrease of the a lattice parameter by approximately 1.2 pm and an increase of the c lattice parameter by about 1.0 pm. The crystal is stressed additionally by adding silicon resulting in a increase of the biaxial compressive stress of up to 2.0 GPa. Further increase of the silicon concentration leads to lattice relaxation. This result from X-ray diffraction was independently confirmed by Raman spectroscopy investigations. Further increase of the silicon concentration leads to the generation of polycrystalline phases within the epitaxial layer. XTEM measurements detected these polycrystalline phases. In addition, XTEM investigations confirmed also the increase of the lateral crystal size with increasing silicon concentration, as well as a great reduction of the screw dislocation density by more than one order of magnitude as found by X-ray diffraction: in undoped, nitrogen rich grown AlN layers the screw dislocation density is about 3 x 10{sup 8} cm{sup -2}, while AlN layers with a silicon concentration of 5 x 10{sup 20} cm{sup -3} show a screw dislocation density of only 1 x 10{sup 7} cm{sup -2}. In low-doped AlN:Si ([Si]{approx}2 x 10{sup 19} cm{sup -3}) the activation energy of the electronic conductivity is about 250 meV. Increasing the silicon concentration to about 1 x 10{sup 21} cm{sup -3} leads to an increase of the activation energy up to more than 500 meV in the now much more stressed AlN:Si epilayer. Studies of the absorption

  15. A DFT study on graphene, SiC, BN, and AlN nanosheets as anodes in Na-ion batteries.

    Science.gov (United States)

    Hosseinian, A; Khosroshahi, E Saedi; Nejati, K; Edjlali, E; Vessally, E

    2017-11-25

    A great concern exists about the lifetime, cost, low-temperature performance, and safety of Li-ion batteries. Na-ion batteries (NIB) are an alternative to the Li-ion batteries due to the wide availability of sodium, its low cost, and nontoxicity. Here, we examined the Na and Na + adsorption on nanosheets of carbon (graphene), AlN, BN, and SiC to explore their potential use as an anode in NIBs. The interaction of atomic Na was found to play the main role in producing different nanosheet cell voltages. Unlike the graphene and SiC nanosheets, the lone pairs on the surface of the AlN and BN nanosheets hinder the Na adsorption and significantly increase the cell voltage. The order of magnitude of the nanosheet cell voltage as an anode in NIBs is as follows: AlN (1.49 V) > BN (1.46 V) > > C (0.69 V) > SiC (0.61 V). The AlN and BN nanosheets may be appropriate compounds for NIBs and their cell voltages are comparable with carbon nanotubes.

  16. Dispersion properties and low infrared optical losses in epitaxial AlN on sapphire substrate in the visible and infrared range

    Czech Academy of Sciences Publication Activity Database

    Soltani, A.; Stolz, A.; Charrier, J.; Mattalah, M.; Gerbedoen, J.-C.; Barkad, H.A.; Mortet, Vincent; Rousseau, M.; Bourzgui, N.; BenMoussa, A.; De Jaeger, J.-C.

    2014-01-01

    Roč. 115, č. 16 (2014), "163515-1"-"163515-6" ISSN 0021-8979 Institutional support: RVO:68378271 Keywords : III-V semiconductors * AlN films * surface scattering * refractive index * optical properties Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.183, year: 2014

  17. Development of AlN and TiB2 Composites with Nb2O5, Y2O3 and ZrO2 as Sintering Aids

    Science.gov (United States)

    González, José C.; Rodríguez, Miguel Á.; Figueroa, Ignacio A.; Villafuerte-Castrejón, María-Elena; Díaz, Gerardo C.

    2017-01-01

    The synthesis of AlN and TiB2 by spark plasma sintering (SPS) and the effect of Nb2O5, Y2O3 and ZrO2 additions on the mechanical properties and densification of the produced composites is reported and discussed. After the SPS process, dense AlN and TiB2 composites with Nb2O5, Y2O3 and ZrO2 were successfully prepared. X-ray diffraction analysis showed that in the AlN composites, the addition of Nb2O5 gives rise to Nb4N3 during sintering. The compound Y3Al5O12 (YAG) was observed as precipitate in the sample with Y2O3. X-ray diffraction analysis of the TiB2 composites showed TiB2 as a single phase in these materials. The maximum Vickers and toughness values were 14.19 ± 1.43 GPa and 27.52 ± 1.75 GPa for the AlN and TiB2 composites, respectively. PMID:28772681

  18. Microstructural analysis in the depth direction of a heteroepitaxial AlN thick film grown on a trench-patterned template by nanobeam X-ray diffraction

    Science.gov (United States)

    Shida, K.; Takeuchi, S.; Tohei, T.; Miyake, H.; Hiramatsu, K.; Sumitani, K.; Imai, Y.; Kimura, S.; Sakai, A.

    2018-04-01

    This work quantitatively assessed the three-dimensional distribution of crystal lattice distortions in an epitaxial AlN thick film grown on a trench-patterned template, using nanobeam X-ray diffraction. Position-dependent ω-2θ-φ mapping clearly demonstrated local tilting, spacing and twisting of lattice planes as well as fluctuations in these phenomena on a sub-micrometer scale comparable to the pitch of the trench-and-terrace patterning. Analysis of the crystal lattice distortion in the depth direction was performed using a newly developed method in which the X-ray nanobeam diffracted from the sample surface to specific depths can be selectively detected by employing a Pt wire profiler. This technique generated depth-resolved ω-2θ-φ maps confirming that fluctuations in lattice plane tilting and spacing greatly depend on the dislocation distribution and the history of the AlN epitaxial growth on the trench-patterned structure. It was also found that both fluctuations were reduced on approaching the AlN surface and, in particular, were sharply reduced at specific depths in the terrace regions. These sharp reductions are attributed to the formation of sacrificial zones with degraded crystal quality around the trenches and possibly lead to raising the crystal quality near the surface of the AlN film.

  19. A first-principles study of the SCN− chemisorption on the surface of AlN, AlP, and BP nanotubes

    International Nuclear Information System (INIS)

    Soltani, Alireza; Taghartapeh, Mohammad Ramezani; Mighani, Hossein; Pahlevani, Amin Allah; Mashkoor, Reza

    2012-01-01

    Graphical abstract: Adsorption properties of SCN − on AlN, AlP, and BP nanotubes based on density functional theory. ▶ We demonstrate the most stable configurations (N-side) of SCN − on AlN, AlP, and BP nanotubes models. Highlights: ► The SCN − Adsorption on surface of AlN, AlP, and BP nanotubes were studied via density functional theory (DFT). ► The interaction of SCN − on the electronic properties and the NBO charge distribution of mentioned configurations are investigated. ► The studies suggest that the adsorption energies of SCN − on AlPNT is most notable in comparison with AlNNT and BPNT. - Abstract: We have performed first-principles calculations to explore the adsorption behavior of the SCN − on electronic properties of AlN, AlP, and BP nanotubes. The adsorption value of SCN − for the most stable formation on the AlPNT is about −318.16 kJ mol −1 , which is reason via the chemisorptions of SCN anion. The computed density of states (DOS) indicates that a notable orbital hybridization take place between SCN − and AlP nanotube in adsorption process. Finally, the AlP nanotube can be used to design as useful sensor for nanodevice applications.

  20. Effects of AlN buffer layers on the structural and the optical properties of GaN epilayers grown on Al2O3 substrates by using plasma-assisted molecular beam epitaxy

    International Nuclear Information System (INIS)

    Jeon, Heechang; Lee, Seungjoo; Kumar, Sunil; Kang, Taewon; Lee, Namhyun; Kim, Taewhan

    2014-01-01

    GaN epilayers on AlN buffer layers with various thicknesses were grown on sapphire substrates by using plasma-assisted molecular-beam epitaxy. The GaN epilayer with an AlN buffer layer was much smaller than the GaN epilayer without an AlN buffer layer. The crystal quality of the GaN active layer was improved by utilizing an AlN layer, which acted as a nucleation layer. The reduced defect density promoted GaN coalition. The double-crystal rocking curves and the photoluminescence spectra showed that the GaN epilayer grown on a 4-nm AlN buffer layer had the best quality among the several kinds of samples. The photoluminescence intensity of the GaN epilayer which is related to the density of the crystal defects was lower when an AlN buffer layer was used the thin AlN nucleation layer protected against stain propagation. These results indicate that GaN epilayers grown on AIN buffer layers hold promise for applications in short-wavelength optoelectronic devices.

  1. Reproductive status and testosterone among females in cooperative mole-rat societies.

    Science.gov (United States)

    Lutermann, Heike; Young, Andrew J; Bennett, Nigel C

    2013-06-15

    Sexual selection acts on traits that increase reproductive success. Variation in reproductive success is often higher among males than females. Consequently, sexual selection has been studied extensively in males while its possible role in females has only recently attracted considerable attention. In some cooperatively breeding species females compete intensely for reproductive opportunities and may thereby have evolved 'male-like' traits such as increased intra-sexual aggression and exaggerated secondary sexual traits. The expression of the latter tends to be testosterone-dependent in male vertebrates but whether this is also the case among females remains poorly understood. Here, we compare two cooperatively breeding mole-rat species (Natal, Cryptomys hottentotus natalensis, and Damaraland mole-rats, Fukomys damarensis) in which a single female monopolises reproduction through behavioural and physiological suppression, respectively, to evaluate the effect of female intra-sexual competition. Consistent with the hypothesis that intra-sexual competition has shaped patterns of testosterone (T) secretion among females in these species, we show that (i) female T levels in both species are significantly higher among breeding (BFs) (who may face the highest degree of intra-sexual competition) compared to non-breeding females (NBFs), (ii) that T levels in both species are significantly higher when access to unrelated males can be assumed to be greatest (i.e., wet season), and (iii) that the average female T levels are a full order of magnitude higher in the absence of a physiological mechanism of reproductive suppression. Together, our results suggest a role for intra-sexual competition in shaping patterns of T secretion among females of the social mole-rats and raise the possibility of a modulatory role for the mode of reproductive suppression on competition-related traits in females. Copyright © 2013 Elsevier Inc. All rights reserved.

  2. Genetic signatures for enhanced olfaction in the African mole-rats.

    Directory of Open Access Journals (Sweden)

    Sofia Stathopoulos

    Full Text Available The Olfactory Receptor (OR superfamily, the largest in the vertebrate genome, is responsible for vertebrate olfaction and is traditionally subdivided into 17 OR families. Recent studies characterising whole-OR subgenomes revealed a 'birth and death' model of evolution for a range of species, however little is known about fine-scale evolutionary dynamics within single-OR families. This study reports the first assessment of fine-scale OR evolution and variation in African mole-rats (Bathyergidae, a family of subterranean rodents endemic to sub-Saharan Africa. Because of the selective pressures of life underground, enhanced olfaction is proposed to be fundamental to the evolutionary success of the Bathyergidae, resulting in a highly diversified OR gene-repertoire. Using a PCR-sequencing approach, we analysed variation in the OR7 family across 14 extant bathyergid species, which revealed enhanced levels of functional polymorphisms concentrated across the receptors' ligand-binding region. We propose that mole-rats are able to recognise a broad range of odorants and that this diversity is reflected throughout their OR7 gene repertoire. Using both classic tests and tree-based methods to test for signals of selection, we investigate evolutionary forces across the mole-rat OR7 gene tree. Four well-supported clades emerged in the OR phylogeny, with varying signals of selection; from neutrality to positive and purifying selection. Bathyergid life-history traits and environmental niche-specialisation are explored as possible drivers of adaptive OR evolution, emerging as non-exclusive contributors to the positive selection observed at OR7 genes. Our results reveal unexpected complexity of evolutionary mechanisms acting within a single OR family, providing insightful perspectives into OR evolutionary dynamics.

  3. Multidimensional MRI-CT atlas of the naked mole-rat brain (Heterocephalus glaber).

    Science.gov (United States)

    Seki, Fumiko; Hikishima, Keigo; Nambu, Sanae; Okanoya, Kazuo; Okano, Hirotaka J; Sasaki, Erika; Miura, Kyoko; Okano, Hideyuki

    2013-01-01

    Naked mole-rats have a variety of distinctive features such as the organization of a hierarchical society (known as eusociality), extraordinary longevity, and cancer resistance; thus, it would be worthwhile investigating these animals in detail. One important task is the preparation of a brain atlas database that provide comprehensive information containing multidimensional data with various image contrasts, which can be achievable using a magnetic resonance imaging (MRI). Advanced MRI techniques such as diffusion tensor imaging (DTI), which generates high contrast images of fiber structures, can characterize unique morphological properties in addition to conventional MRI. To obtain high spatial resolution images, MR histology, DTI, and X-ray computed tomography were performed on the fixed adult brain. Skull and brain structures were segmented as well as reconstructed in stereotaxic coordinates. Data were also acquired for the neonatal brain to allow developmental changes to be observed. Moreover, in vivo imaging of naked mole-rats was established as an evaluation tool of live animals. The data obtained comprised three-dimensional (3D) images with high tissue contrast as well as stereotaxic coordinates. Developmental differences in the visual system were highlighted in particular by DTI. Although it was difficult to delineate optic nerves in the mature adult brain, parts of them could be distinguished in the immature neonatal brain. From observation of cortical thickness, possibility of high somatosensory system development replaced to the visual system was indicated. 3D visualization of brain structures in the atlas as well as the establishment of in vivo imaging would promote neuroimaging researches towards detection of novel characteristics of eusocial naked mole-rats.

  4. Multidimensional MRI-CT atlas of the naked mole-rat brain

    Directory of Open Access Journals (Sweden)

    Fumiko eSeki

    2013-12-01

    Full Text Available Naked mole-rats have a variety of distinctive features such as the organisation of a hierarchical society (known as eusociality, extraordinary longevity, and cancer resistance; thus, it would be worthwhile investigating these animals in detail. One important task is the preparation of a brain atlas database that provide comprehensive information containing multidimensional data with various image contrasts, which can be achievable using a magnetic resonance imaging (MRI. Advanced MRI techniques such as diffusion tensor imaging (DTI, which generates high contrast images of fibre structures, can characterise unique morphological properties in addition to conventional MRI. To obtain high spatial resolution images, MR histology, DTI, and X-ray computed tomography (CT were performed on the fixed adult brain. Skull and brain structures were segmented as well as reconstructed in stereotaxic coordinates. Data were also acquired for the neonatal brain to allow developmental changes to be observed. Moreover, in vivo imaging of naked mole-rats was established as an evaluation tool of live animals. The data obtained comprised three-dimensional (3D images with high tissue contrast as well as stereotaxic coordinates. Developmental differences in the visual system were highlighted in particular by DTI. Although it was difficult to delineate optic nerves in the mature adult brain, parts of them could be distinguished in the immature neonatal brain. From observation of cortical thickness, possibility of high somatosensory system development replaced to the visual system was indicated. 3D visualisation of brain structures in the atlas as well as the establishment of in vivo imaging would promote neuroimaging researches towards detection of novel characteristics of eusocial naked mole-rats.

  5. Effect of combining imidacloprid and diatomaceous earth with Beauveria bassiana on mole cricket (Orthoptera: Gryllotalpidae) mortality.

    Science.gov (United States)

    Thompson, Sarah R; Brandenburg, Rick L

    2006-12-01

    Sublethal doses of three orthopteran-derived strains of Beauveria bassiana (Balsamo) Vuillemin were topically applied to adult southern mole crickets, Scapteriscus borellii Giglio-Tos (Orthoptera: Gryllotalpidae), and tested in combination with substrate treatments of diatomaceous earth (DE) and imidacloprid. Crickets treated only with the high doses (10(8) conidia per cricket) of each of the three B. bassiana strains exhibited the shortest survival times as well as the highest percentage mortality at 28 d after treatment. However, these treatments did.not differ significantly from any of the diatomaceous earth combination treatments. Two of the strains tested, 5977 and 3622, exhibited synergistic interactions with DE, whereas the third strain, GHA, was not significant for synergy. Mortality caused by the combination treatment was still greater than the expected additive effect. DE abrades the insect cuticle and absorbs cuticular lipids, aiding the entry of germinating conidia into the mole cricket hemocoel. None of the three strains exhibited synergy when combined with imidacloprid, and mortality of all combination treatments was less than additive. For strain 5977, there was an antagonistic interaction with imidacloprid. It was difficult to obtain <30% mortality for imidacloprid only treatments, which was considered the upper limit for sublethal doses. The mean percentage mortality caused by imidacloprid was 37.5%, and this high percentage made it difficult for any combination treatment to cause significantly more mortality than the expected additive effect. These results clarify the interactions of other control products with B. bassiana and provide a basis for a reduced pesticide approach to mole cricket control.

  6. Cleaning the IceMole: collection of englacial samples from Blood Falls, Antarctica

    Science.gov (United States)

    Mikucki, J.; Digel, I.; Chua, M.; Davis, J.; Ghosh, D.; Lyons, W. B.; Welch, K. A.; Purcell, A.; Francke, G.; Feldmann, M.; Espe, C.; Heinen, D.; Dachwald, B.; Kowalski, J.; Tulaczyk, S. M.

    2016-12-01

    The Minimally Invasive Direct Glacial Access project (MIDGE) used a maneuverable thermoelectric melting probe called the IceMole to collect the first englacial samples of brine from Blood Falls, Antarctica. In order to maintain the scientific integrity of samples collected and minimize impact to this specially protected ecosystem, microbial and chemical contamination of the IceMole needed to be minimized. Guidelines have been established for research in Antarctic subglacial systems by the scientific and regulatory community and have been detailed by the "Code of Conduct for the Exploration and Research of Subglacial Aquatic Environments" put forth by the Scientific Committee on Antarctic Research (SCAR) Action Group, and was submitted to the Antarctic Treaty System. This Code of Conduct (CoC) recognizes the ecological importance and pristine nature of subglacial habitats and recommends a path forward towards clean exploration. Similarly, the US and European space agencies (NASA and ESA) have detailed instrument preparation protocols for the exploration of icy worlds in our solar system for planetary protection. Given the synergistic aims of these two groups we have adopted protocols from both subglacial and space exploration approaches. Here we present our approach to cleaning the IceMole in the field and report on ability to reduce the bioload inherent on the melter. Specifically our protocol reduced the exterior bio-load by an order of magnitude, to levels common in most clean rooms, and 1-3 orders of magnitude below that of Taylor Glacier ice surrounding Blood Falls. Our results indicate that the collection of englacial samples for microbiological analysis is feasible with melting probes.

  7. Naked mole-rat acid-sensing ion channel 3 forms nonfunctional homomers, but functional heteromers.

    Science.gov (United States)

    Schuhmacher, Laura-Nadine; Callejo, Gerard; Srivats, Shyam; Smith, Ewan St John

    2018-02-02

    Acid-sensing ion channels (ASICs) form both homotrimeric and heterotrimeric ion channels that are activated by extracellular protons and are involved in a wide range of physiological and pathophysiological processes, including pain and anxiety. ASIC proteins can form both homotrimeric and heterotrimeric ion channels. The ASIC3 subunit has been shown to be of particular importance in the peripheral nervous system with pharmacological and genetic manipulations demonstrating a role in pain. Naked mole-rats, despite having functional ASICs, are insensitive to acid as a noxious stimulus and show diminished avoidance of acidic fumes, ammonia, and carbon dioxide. Here we cloned naked mole-rat ASIC3 (nmrASIC3) and used a cell-surface biotinylation assay to demonstrate that it traffics to the plasma membrane, but using whole-cell patch clamp electrophysiology we observed that nmrASIC3 is insensitive to both protons and the non-proton ASIC3 agonist 2-guanidine-4-methylquinazoline. However, in line with previous reports of ASIC3 mRNA expression in dorsal root ganglia neurons, we found that the ASIC3 antagonist APETx2 reversibly inhibits ASIC-like currents in naked mole-rat dorsal root ganglia neurons. We further show that like the proton-insensitive ASIC2b and ASIC4, nmrASIC3 forms functional, proton-sensitive heteromers with other ASIC subunits. An amino acid alignment of ASIC3s between 9 relevant rodent species and human identified unique sequence differences that might underlie the proton insensitivity of nmrASIC3. However, introducing nmrASIC3 differences into rat ASIC3 (rASIC3) produced only minor differences in channel function, and replacing the nmrASIC3 sequence with that of rASIC3 did not produce a proton-sensitive ion channel. Our observation that nmrASIC3 forms nonfunctional homomers may reflect a further adaptation of the naked mole-rat to living in an environment with high-carbon dioxide levels. © 2018 by The American Society for Biochemistry and Molecular

  8. Mechanisms regulating proteostasis are involved in sympatric speciation of the blind mole rat, Spalax galili.

    Science.gov (United States)

    Rodriguez, Karl A; Li, Kexin; Nevo, Eviatar; Buffenstein, Rochelle

    2016-01-01

    Genome-wide analysis demonstrates extensive genomic adaptive complexes involved in sympatric speciation between blind mole rats (Spalax galili) in abutting populations living in basalt and chalk soils. Among the gene ontology (GO) enrichment, musculature and metabolism stood out in basalt dwellers while nutrition and neurogenetics were highlighted in chalk residents. Measurements of mechanisms regulating protein homeostasis inspired by these GO terms suggest that at the proteomic level there is also a habitat/soil-type driven divergence with the basalt residents exhibiting higher proteasome activity whereas elevated levels of markers of autophagy are evident in the chalk inhabitants.

  9. Ultrasound imaging of partial hydatidiform mole in the second trimester of pregnancy

    International Nuclear Information System (INIS)

    Jover Labiste, Marina

    2012-01-01

    The case report of a 27 year-old patient with 18 weeks gestation, admitted to the Obstetrics Department of 'Mariana Grajales Coello' Provincial Gynecology and Obstetrics Hospital of Santiago de Cuba due to high blood pressure, cephalea and pain in lower abdomen is described. Additional tests confirmed a partial hydatidiform mole, so that uterine curettage was performed and small fragments of endometrial stroma were removed for pathological study. Outpatient medical monitoring was recommended and the patient had an appointment at 21 days for controlling and evaluating her general state

  10. Absence of histamine-induced itch in the African naked mole-rat and "rescue" by Substance P.

    Science.gov (United States)

    Smith, Ewan St John; Blass, Gregory R C; Lewin, Gary R; Park, Thomas J

    2010-05-24

    Recent research has proposed a pathway in which sensory neurons expressing the capsaicin activated ion channel TRPV1 are required for histamine-induced itch and subsequent scratching behavior. We examined histamine-induced itch in the African naked mole-rat (Heterocephalus glaber) and found that although naked mole-rats display innate scratching behavior, histamine was unable to evoke increased scratching as is observed in most mouse strains. Using calcium imaging, we examined the histamine sensitivity of naked mole-rat dorsal root ganglia (DRG) neurons and identified a population of small diameter neurons activated by histamine, the majority of which are also capsaicin-sensitive. This suggested that naked mole-rat sensory neurons are activated by histamine, but that spinal dorsal horn processing of sensory information is not the same as in other rodents. We have previously shown that naked mole-rats naturally lack substance P (SP) in cutaneous C-fibers, but that the neurokinin-1 receptor is expressed in the superficial spinal cord. This led us to investigate if SP deficiency plays a role in the lack of histamine-induced scratching in this species. After intrathecal administration of SP into the spinal cord we observed robust scratching behavior in response to histamine injection. Our data therefore support a model in which TRPV1-expressing sensory neurons are important for histamine-induced itch. In addition, we demonstrate a requirement for active, SP-induced post-synaptic drive to enable histamine sensitive afferents to drive itch-related behavior in the naked mole-rat. These results illustrate that it is altered dorsal horn connectivity of nociceptors that underlies the lack of itch and pain-related behavior in the naked mole-rat.

  11. Absence of histamine-induced itch in the African naked mole-rat and "rescue" by Substance P

    Directory of Open Access Journals (Sweden)

    Lewin Gary R

    2010-05-01

    Full Text Available Abstract Recent research has proposed a pathway in which sensory neurons expressing the capsaicin activated ion channel TRPV1 are required for histamine-induced itch and subsequent scratching behavior. We examined histamine-induced itch in the African naked mole-rat (Heterocephalus glaber and found that although naked mole-rats display innate scratching behavior, histamine was unable to evoke increased scratching as is observed in most mouse strains. Using calcium imaging, we examined the histamine sensitivity of naked mole-rat dorsal root ganglia (DRG neurons and identified a population of small diameter neurons activated by histamine, the majority of which are also capsaicin-sensitive. This suggested that naked mole-rat sensory neurons are activated by histamine, but that spinal dorsal horn processing of sensory information is not the same as in other rodents. We have previously shown that naked mole-rats naturally lack substance P (SP in cutaneous C-fibers, but that the neurokinin-1 receptor is expressed in the superficial spinal cord. This led us to investigate if SP deficiency plays a role in the lack of histamine-induced scratching in this species. After intrathecal administration of SP into the spinal cord we observed robust scratching behavior in response to histamine injection. Our data therefore support a model in which TRPV1-expressing sensory neurons are important for histamine-induced itch. In addition, we demonstrate a requirement for active, SP-induced post-synaptic drive to enable histamine sensitive afferents to drive itch-related behavior in the naked mole-rat. These results illustrate that it is altered dorsal horn connectivity of nociceptors that underlies the lack of itch and pain-related behavior in the naked mole-rat.

  12. Cholecalciferol has no effect on calcium and inorganic phosphorus balance in a naturally cholecalciferol-deplete subterranean mammal, the naked mole rat (Heterocephalus glaber).

    Science.gov (United States)

    Buffenstein, R; Yahav, S

    1991-04-01

    Naked mole rats, Heterocephalus glaber, have no obvious source of cholecalciferol (D3) available to them, given their underground habitat and tubiferous diet. They have undetectable levels of 25-OH-D3 and as such appear to be naturally deplete in D3. The effect of an oral D3 supplement on mineral balance and homeostasis was therefore investigated. This D3 treatment did not affect circulating levels of Ca2+ and inorganic phosphorus (P(i]. Nor did D3 treatment affect mineral intake and absorption. The Ca2+ and P(i) present in the food was efficiently extracted and absorbed, resulting in an apparent fractional absorption (AFA) efficiency exceeding 98%. Irrespective of D3 treatment, the amount of Ca2+ and P(i) absorbed was positively correlated with the amount ingested, suggesting that intestinal uptake is by a passive D3-independent process. After D3 supplementation urinary Ca2+ secretion was unchanged; however, the amount of P(i) excreted in the urine increased (P less than or equal to 0.05). This resulted in a concomitant decline in P(i) AFR (P less than or equal to 0.02 from 99.95 +/- 0.02% to 99.82 +/- 0.03%). Almost all the Ca2+ and P(i) in the glomerular filtrate were reabsorbed, facilitating AFR efficiencies that approach physiological maxima (greater than 99%). Changes in AFR efficiency with D3 supplementation are therefore of no biological significance. Net mineral flux of both elements, irrespective of D3 treatment, was positive. It is speculated that the ever-growing incisors of these animals act as mineral dumps and assist in the tight regulation of plasma Ca2+ and P(i). These data suggest that naked mole rats utilize mechanisms independent of D3 in regulating mineral homeostasis and are therefore well-adapted to an environment devoid of sunlight.

  13. Reproduction, aging and mortality rate in social subterranean mole voles (Ellobius talpinus Pall.).

    Science.gov (United States)

    Novikov, E; Kondratyuk, E; Petrovski, D; Titova, T; Zadubrovskaya, I; Zadubrovskiy, P; Moshkin, M

    2015-12-01

    Eusocial subterranean rodents of the Bathyergidae family have enormous longevity. The long lifespan of these species is associated with negligible senescence, that is, an absence of the signs of age-related deterioration in physical condition. The question arises as to whether these features are unique to eusocial Bathyergids or typical of other social subterranean rodents as well. In the present study, we analysed data from observations of a social subterranean Microtinae rodent, the northern mole vole (Ellobius talpinus Pall.), which, like mole-rats, has reproductive skew. Among the individuals captured in the wild and maintained in captivity, females that reproduced lived significantly longer than non-breeding females. We did not find any changes in muscle strength with age in any of the demographic groups studied. Faecal glucocorticoid concentrations before death were significantly higher in non-breeding females than in breeding females and males. Increased adrenocortical activity may be one mechanism responsible for the decreased lifespan of non-reproducing individuals of social subterranean rodents. We conclude that the patterns of aging, although different in some respects, are generally common for social subterranean rodents of different taxonomic groups.

  14. Uterine rupture in twin pregnancy with normal fetus and complete hydatidiform mole.

    Science.gov (United States)

    Sánchez-Ferrer, María Luisa; Hernández-Martínez, Florentina; Machado-Linde, Francisco; Ferri, Belén; Carbonel, Pablo; Nieto-Diaz, Anibal

    2014-01-01

    We describe a rare case of complete hydatidiform mole with twin live fetus (CHMTF) confirmed by histopathology, flow cytometry and polymerase chain reaction techniques. No malformations were observed, fetal karyotype was normal and β-human chorionic gonadotropin levels were high (>100,000 IU/ml). The patient was informed of the risks and decided to continue with the pregnancy, but at week 15, she had to undergo hysterectomy due to uterine rupture. She subsequently developed persistent trophoblastic disease (PTD) with pulmonary metastases that required treatment with polychemotherapy. Patients with CHMTF should be informed of all known risks, including the considerable risk of PTD, which is similar to or, even higher than that associated with a singleton complete mole. The risk does not appear to be increased by continuing the pregnancy. Because so few series have been published, there is a lack of evidence-based clinical management guidelines. To our knowledge, this is the first report of uterine rupture in CHMTF. © 2013 S. Karger AG, Basel.

  15. Adaptations to a Subterranean Environment and Longevity Revealed by the Analysis of Mole Rat Genomes

    Directory of Open Access Journals (Sweden)

    Xiaodong Fang

    2014-09-01

    Full Text Available Subterranean mammals spend their lives in dark, unventilated environments that are rich in carbon dioxide and ammonia and low in oxygen. Many of these animals are also long-lived and exhibit reduced aging-associated diseases, such as neurodegenerative disorders and cancer. We sequenced the genome of the Damaraland mole rat (DMR, Fukomys damarensis and improved the genome assembly of the naked mole rat (NMR, Heterocephalus glaber. Comparative genome analyses, along with the transcriptomes of related subterranean rodents, revealed candidate molecular adaptations for subterranean life and longevity, including a divergent insulin peptide, expression of oxygen-carrying globins in the brain, prevention of high CO2-induced pain perception, and enhanced ammonia detoxification. Juxtaposition of the genomes of DMR and other more conventional animals with the genome of NMR revealed several truly exceptional NMR features: unusual thermogenesis, an aberrant melatonin system, pain insensitivity, and unique processing of 28S rRNA. Together, these genomes and transcriptomes extend our understanding of subterranean adaptations, stress resistance, and longevity.

  16. Androgen receptor distribution in the social decision-making network of eusocial naked mole-rats.

    Science.gov (United States)

    Holmes, Melissa M; Van Mil, Spencer; Bulkowski, Camila; Goldman, Sharry L; Goldman, Bruce D; Forger, Nancy G

    2013-11-01

    Naked mole-rats are highly social rodents that live in large groups and exhibit a strict reproductive and social hierarchy. Only a few animals in each colony breed; the remainder are non-reproductive and are socially subordinate to breeders. We have examined androgen receptor immunoreactive (AR+) cells in brain regions comprising the recently described social decision-making network in subordinate and breeder naked mole-rats of both sexes. We find that subordinates have a significantly higher percentage of AR+ cells in all brain regions expressing this protein. By contrast, there were no significant effects of sex and no sex-by-status interactions on the percentage of AR+ cells. Taken together with previous findings, the present data complete a systematic assessment of the distribution of AR protein in the social decision-making network of the eusocial mammalian brain and demonstrate a significant role for social status in the regulation of this protein throughout many nodes of this network. Copyright © 2013 Elsevier B.V. All rights reserved.

  17. Differential effects of chronic fluoxetine on the behavior of dominant and subordinate naked mole-rats.

    Science.gov (United States)

    Mongillo, Daniel L; Kosyachkova, Ekaterina A; Nguyen, Tam M; Holmes, Melissa M

    2014-01-01

    Naked mole-rats are eusocial rodents that live in large subterranean colonies with a strict reproductive and social hierarchy. The breeding female (referred to as the queen) and 1 to 3 breeding males are the only reproductive members of the colony. Breeders are socially dominant and all other colony members are non-reproductive subordinates. The effects of manipulating the serotonergic neurotransmitter system on aggression and dominance behaviors are well studied in many species, but not in eusocial rodents like the naked mole-rat. The current study investigated how the serotonergic system influences aggressive/dominant behaviors in this species. To do this, two separate but related experiments were conducted: the effects of fluoxetine hydrochloride (FLX) on status-specific behaviors of subordinates (Experiment 1) and dominant queens (Experiment 2) were evaluated both in-colony and in a social-pairing paradigm. In accordance with our main hypothesis, chronic treatment of FLX attenuated the frequency and duration of aggression in queens, but not subordinates, when paired with an unfamiliar conspecific. Further exploration of pharmacological manipulation on status-specific behaviors of this eusocial species may elucidate the neurobiological mechanisms underlying their unique and rigid social hierarchy. Copyright © 2013 Elsevier B.V. All rights reserved.

  18. Retinal ganglion cell survival and axon regeneration after optic nerve injury in naked mole-rats.

    Science.gov (United States)

    Park, Kevin K; Luo, Xueting; Mooney, Skyler J; Yungher, Benjamin J; Belin, Stephane; Wang, Chen; Holmes, Melissa M; He, Zhigang

    2017-02-01

    In the adult mammalian central nervous system (CNS), axonal damage often triggers neuronal cell death and glial activation, with very limited spontaneous axon regeneration. In this study, we performed optic nerve injury in adult naked mole-rats, the longest living rodent, with a maximum life span exceeding 30 years, and found that injury responses in this species are quite distinct from those in other mammalian species. In contrast to what is seen in other mammals, the majority of injured retinal ganglion cells (RGCs) survive with relatively high spontaneous axon regeneration. Furthermore, injured RGCs display activated signal transducer and activator of transcription-3 (STAT3), whereas astrocytes in the optic nerve robustly occupy and fill the lesion area days after injury. These neuron-intrinsic and -extrinsic injury responses are reminiscent of those in "cold-blooded" animals, such as fish and amphibians, suggesting that the naked mole-rat is a powerful model for exploring the mechanisms of neuronal injury responses and axon regeneration in mammals. J. Comp. Neurol. 525:380-388, 2017. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

  19. Endocrine function and neurobiology of the longest-living rodent, the naked mole-rat.

    Science.gov (United States)

    Edrey, Yael H; Park, Thomas J; Kang, Hyesin; Biney, Adriana; Buffenstein, Rochelle

    2011-01-01

    Animals that have evolved exceptional capabilities, such as extraordinary longevity may reveal pertinent and potentially critical insights into biomedical research that are not readily apparent in standard laboratory animals. Naked mole-rats (Heterocephalus glaber; NMRs) are extremely long-lived (30 years) mouse-sized rodents. They clearly have evolved superior anti-aging mechanisms as evident by the markedly attenuated age-related decline in physiological function, sustained reproductive capacity and pronounced cancer resistance throughout their long-lives. These eusocial rodents, like the social insects, live in colonies with breeding restricted to one female and a few males. Subordinates are sexually monomorphic, yet retain the ability to become breeders, and can undergo growth surges and neural modifications at any time throughout their life. This plasticity in physiological and behavioral aspects may have contributed to their long-lives. Naked mole-rats show numerous adaptations to life underground including extreme tolerance of hypoxia, acid insensitivity, as well as independence of photoendocrine systems. Here we review what is known about their unique social structure, sensory systems, endocrinology and neurobiology, and highlight areas that may be pertinent to biogerontology. Copyright © 2010 Elsevier Inc. All rights reserved.

  20. Dominance and queen succession in captive colonies of the eusocial naked mole-rat, Heterocephalus glaber.

    Science.gov (United States)

    Clarke, F M; Faulkes, C G

    1997-07-22

    Naked mole-rat colonies exhibit a high reproductive skew, breeding being typically restricted to one female (the 'queen') and one to three males. Other colony members are reproductively suppressed, although this suppression can be reversed following the removal or death of the queen. We examined dominance and queen succession within captive colonies to investigate the relationship between urinary testosterone and cortisol, dominance rank and reproductive status; and to determine if behavioural and/or physiological parameters can be used as predictors of queen succession. Social structure was characterized by a linear dominance hierarchy before and after queen removal. Prior to queen removal, dominance rank was negatively correlated with body weight and urinary testosterone and cortisol titres in males and females. Queen removal results in social instability and aggression between high ranking individuals. Dominance rank appears to be a good predictor of reproductive status: queens are the highest ranking colony females and are succeeded by the next highest ranking females. The intense dominance-related aggression that accompanies reproductive succession in naked mole-rats provides empirical support for optimal skew theory.

  1. Initialized Fractional Calculus

    Science.gov (United States)

    Lorenzo, Carl F.; Hartley, Tom T.

    2000-01-01

    This paper demonstrates the need for a nonconstant initialization for the fractional calculus and establishes a basic definition set for the initialized fractional differintegral. This definition set allows the formalization of an initialized fractional calculus. Two basis calculi are considered; the Riemann-Liouville and the Grunwald fractional calculi. Two forms of initialization, terminal and side are developed.

  2. Community structure variability of Uropodina mites (Acari: Mesostigmata) in nests of the common mole, Talpa europaea, in Central Europe.

    Science.gov (United States)

    Napierała, Agnieszka; Mądra, Anna; Leszczyńska-Deja, Kornelia; Gwiazdowicz, Dariusz J; Gołdyn, Bartłomiej; Błoszyk, Jerzy

    2016-04-01

    Underground nests of Talpa europaea, known as the common mole, are very specific microhabitats, which are also quite often inhabited by various groups of arthropods. Mites from the suborder Uropodina (Acari: Mesostigmata) are only one of them. One could expect that mole nests that are closely located are inhabited by communities of arthropods with similar species composition and structure. However, results of empirical studies clearly show that even nests which are close to each other can be different both in terms of the species composition and abundance of Uropodina communities. So far, little is known about the factors that can cause these differences. The major aim of this study was to identify factors determining species composition, abundance, and community structure of Uropodina communities in mole nests. The study is based on material collected during a long-term investigation conducted in western parts of Poland. The results indicate that the two most important factors influencing species composition and abundance of Uropodina communities in mole nests are nest-building material and depth at which nests are located. Composition of Uropodina communities in nests of moles was also compared with that of other microhabitats (e.g. rotten wood, forest litter, soil) based on data from 4421 samples collected in Poland. Communities of this habitat prove most similar to these of open areas, especially meadows, as well as some forest types.

  3. A stable algorithm for calculating phase equilibria with capillarity at specified moles, volume and temperature using a dynamic model

    KAUST Repository

    Kou, Jisheng

    2017-09-30

    Capillary pressure can significantly affect the phase properties and flow of liquid-gas fluids in porous media, and thus, the phase equilibrium calculation incorporating capillary pressure is crucial to simulate such problems accurately. Recently, the phase equilibrium calculation at specified moles, volume and temperature (NVT-flash) becomes an attractive issue. In this paper, capillarity is incorporated into the phase equilibrium calculation at specified moles, volume and temperature. A dynamical model for such problem is developed for the first time by using the laws of thermodynamics and Onsager\\'s reciprocal principle. This model consists of the evolutionary equations for moles and volume, and it can characterize the evolutionary process from a non-equilibrium state to an equilibrium state in the presence of capillarity effect at specified moles, volume and temperature. The phase equilibrium equations are naturally derived. To simulate the proposed dynamical model efficiently, we adopt the convex-concave splitting of the total Helmholtz energy, and propose a thermodynamically stable numerical algorithm, which is proved to preserve the second law of thermodynamics at the discrete level. Using the thermodynamical relations, we derive a phase stability condition with capillarity effect at specified moles, volume and temperature. Moreover, we propose a stable numerical algorithm for the phase stability testing, which can provide the feasible initial conditions. The performance of the proposed methods in predicting phase properties under capillarity effect is demonstrated on various cases of pure substance and mixture systems.

  4. Room-temperature ferromagnetism with high magnetic moment in Cu-doped AlN single crystal whiskers

    Science.gov (United States)

    Jiang, Liang-Bao; Liu, Yu; Zuo, Si-Bin; Wang, Wen-Jun

    2015-02-01

    Ferromagnetism is investigated in high-quality Cu-doped AlN single crystal whiskers. The whiskers exhibit room-temperature ferromagnetism with a magnetic moment close to the results from first-principles calculations. High crystallinity and low Cu concentrations are found to be indispensable for high magnetic moments. The difference between the experimental and theoretical moment values is explored in terms of the influence of nitrogen vacancies. The calculated results demonstrate that nitrogen vacancies can reduce the magnetic moments of Cu atom. Project supported by the National Basic Research Program of China (Grant No. 2013CB932901), the National Natural Science Foundation of China (Grant Nos. 51372267, 51210105026, and 51172270), the Funds from the Chinese Academy of Sciences, the International Centre for Diffraction Data, USA (2013 Ludo Frevel Crystallography Scholarship Award), and the Funds from the Ministry of Education of China (2012 Academic Scholarship Award for Doctoral Candidates).

  5. Effect of (Ti, Al)N Nanostructured Arc-Coatings on Wear and Corrosion Properties of 4340 Alloy Steel.

    Science.gov (United States)

    Hsu, Cheng-Hsun; Lin, Chung-Kwei; Huang, Wei-Che; Lai, Dai-Wei

    2018-04-01

    This study utilized cathodic arc deposition technology to coat Ti-Al-N hard films on AISI 4340 alloy steel. Composition, morphology, and structure of the coatings were analyzed using EPMA, FESEM, XRD, and TEM. Both wear tests and polarization tests were conducted to determine the abrasion and corrosion properties of the steel before and after coating. The results showed that a specific (Ti, Al)N nanostructured multilayer was synthesized smoothly. The multilayer consisted of 10 nm-TiN and 15 nm-TiAlN interaction layers. The coating not only greatly reduced the friction coefficient of AISI 4340 alloy steel from 0.81 to 0.45, but also provided an effective improvement in corrosion resistance.

  6. Synthesis and Characterization of ZnO Nanoflowers Grown on AlN Films by Solution Deposition

    International Nuclear Information System (INIS)

    Hai-Yong, Gao; Fa-Wang, Yan; Yang, Zhang; Jin-Min, Li; Yi-Ping, Zeng

    2008-01-01

    ZnO nanoflowers are synthesized on AlN films by solution method. The synthesized nanoflowers are composed of nanorods, which are pyramidal and grow from a central point, thus forming structures that are flower-shaped as a whole. The nanoflowers have two typical morphologies: plate-like and bush-like. The XRD spectrum corresponds to the side planes of the ZnO nanorods made up of the nanoflowers. The micro-Raman spectrum of the ZnO nanoflowers exhibits the E 2 (high) mode and the second order multiple-phonon mode. The photoluminescence spectrum of the ZnO nanoflowers exhibits ultraviolet emission centred at 375 nm and a broad green emission centred at 526 nm

  7. Spin-Filtering Effects in Wurtzite and Graphite-Like AlN Nano wires with Mn Impurities

    International Nuclear Information System (INIS)

    Nemnes, G.A.

    2013-01-01

    Spin transport properties of magnetic nano wire systems —atomic-sized AlN nano wires with additional Mn impurities—are investigated employing ab initio constrained spin density functional theory calculations and nonequilibrium Green’s functions formalism. The analyzed nano wire structures exhibit a stress-induced phase transition, between wurtzite and graphite-like configurations. In these quasi-one dimensional systems, the surface states ensure the basic prerequisite in establishing spin and charge transfer, by reducing the relatively large bandgap of the group III nitride semiconductor. The results show in how far this phase transition affects the surface states, focusing on the consequences which appear in the spin-filtering processes.

  8. Tempered fractional calculus

    Science.gov (United States)

    Sabzikar, Farzad; Meerschaert, Mark M.; Chen, Jinghua

    2015-07-01

    Fractional derivatives and integrals are convolutions with a power law. Multiplying by an exponential factor leads to tempered fractional derivatives and integrals. Tempered fractional diffusion equations, where the usual second derivative in space is replaced by a tempered fractional derivative, govern the limits of random walk models with an exponentially tempered power law jump distribution. The limiting tempered stable probability densities exhibit semi-heavy tails, which are commonly observed in finance. Tempered power law waiting times lead to tempered fractional time derivatives, which have proven useful in geophysics. The tempered fractional derivative or integral of a Brownian motion, called a tempered fractional Brownian motion, can exhibit semi-long range dependence. The increments of this process, called tempered fractional Gaussian noise, provide a useful new stochastic model for wind speed data. A tempered fractional difference forms the basis for numerical methods to solve tempered fractional diffusion equations, and it also provides a useful new correlation model in time series.

  9. Tempered fractional calculus

    Energy Technology Data Exchange (ETDEWEB)

    Sabzikar, Farzad, E-mail: sabzika2@stt.msu.edu [Department of Statistics and Probability, Michigan State University, East Lansing, MI 48823 (United States); Meerschaert, Mark M., E-mail: mcubed@stt.msu.edu [Department of Statistics and Probability, Michigan State University, East Lansing, MI 48823 (United States); Chen, Jinghua, E-mail: cjhdzdz@163.com [School of Sciences, Jimei University, Xiamen, Fujian, 361021 (China)

    2015-07-15

    Fractional derivatives and integrals are convolutions with a power law. Multiplying by an exponential factor leads to tempered fractional derivatives and integrals. Tempered fractional diffusion equations, where the usual second derivative in space is replaced by a tempered fractional derivative, govern the limits of random walk models with an exponentially tempered power law jump distribution. The limiting tempered stable probability densities exhibit semi-heavy tails, which are commonly observed in finance. Tempered power law waiting times lead to tempered fractional time derivatives, which have proven useful in geophysics. The tempered fractional derivative or integral of a Brownian motion, called a tempered fractional Brownian motion, can exhibit semi-long range dependence. The increments of this process, called tempered fractional Gaussian noise, provide a useful new stochastic model for wind speed data. A tempered fractional difference forms the basis for numerical methods to solve tempered fractional diffusion equations, and it also provides a useful new correlation model in time series.

  10. Antioxidant activity and prevention of pork meat lipid oxidation using traditional Mexican condiments (pasilla dry pepper, achiote, and mole sauce

    Directory of Open Access Journals (Sweden)

    Emilio Alvarez-Parrilla

    2014-06-01

    Full Text Available Considering the extensive use of hot peppers and spicy sauces in the Mexican cuisine, in the present paper, three widely consumed Mexican condiments (mole sauce, achiote, and pasilla hot pepper were analyzed for their total phenols, flavonoids and proanthocyanidins, antioxidant activity, and protective effect against lipid oxidation in chopped pork meat. All samples were extracted first with methanol and then with acetone, and the extracts were compared. Pasilla pepper showed the highest phenolic and flavonoid content in both solvents, followed by mole and achiote. Achiote showed the highest proanthocyanidin concentration. All samples showed high antioxidant activity, and good correlations with phenolic compounds and flavonoids, while no correlation was observed in the case of condensed tannins. Mole sauce methanolic extract showed the highest inhibition of pork meat oxidation, followed by pasilla pepper, and finally achiote paste extracts. These results suggest that these condiments are useful to prevent meat lipid oxidation during storage.

  11. Zigzag and Helical AlN Layer Prepared by Glancing Angle Deposition and Its Application as a Buffer Layer in a GaN-Based Light-Emitting Diode

    Directory of Open Access Journals (Sweden)

    Lung-Chien Chen

    2012-01-01

    Full Text Available This study investigates an aluminum nitride (AlN nanorod structure sputtered by glancing angle deposition (GLAD and its application as a buffer layer for GaN-based light-emitting diodes (LEDs that are fabricated on sapphire substrates. The ray tracing method is adopted with a three-dimensional model in TracePro software. Simulation results indicate that the zigzag AlN nanorod structure is an optimal buffer layer in a GaN-based LED. Furthermore, the light output power of a GaN-based LED with a zigzag AlN nanorod structure improves to as much as 28.6% at a forward current of 20 mA over that of the GaN-based LED with a normal AlN buffer layer.

  12. TEMPERED FRACTIONAL CALCULUS

    Science.gov (United States)

    MEERSCHAERT, MARK M.; SABZIKAR, FARZAD; CHEN, JINGHUA

    2014-01-01

    Fractional derivatives and integrals are convolutions with a power law. Multiplying by an exponential factor leads to tempered fractional derivatives and integrals. Tempered fractional diffusion equations, where the usual second derivative in space is replaced by a tempered fractional derivative, govern the limits of random walk models with an exponentially tempered power law jump distribution. The limiting tempered stable probability densities exhibit semi-heavy tails, which are commonly observed in finance. Tempered power law waiting times lead to tempered fractional time derivatives, which have proven useful in geophysics. The tempered fractional derivative or integral of a Brownian motion, called a tempered fractional Brownian motion, can exhibit semi-long range dependence. The increments of this process, called tempered fractional Gaussian noise, provide a useful new stochastic model for wind speed data. A tempered difference forms the basis for numerical methods to solve tempered fractional diffusion equations, and it also provides a useful new correlation model in time series. PMID:26085690

  13. TEMPERED FRACTIONAL CALCULUS.

    Science.gov (United States)

    Meerschaert, Mark M; Sabzikar, Farzad; Chen, Jinghua

    2015-07-15

    Fractional derivatives and integrals are convolutions with a power law. Multiplying by an exponential factor leads to tempered fractional derivatives and integrals. Tempered fractional diffusion equations, where the usual second derivative in space is replaced by a tempered fractional derivative, govern the limits of random walk models with an exponentially tempered power law jump distribution. The limiting tempered stable probability densities exhibit semi-heavy tails, which are commonly observed in finance. Tempered power law waiting times lead to tempered fractional time derivatives, which have proven useful in geophysics. The tempered fractional derivative or integral of a Brownian motion, called a tempered fractional Brownian motion, can exhibit semi-long range dependence. The increments of this process, called tempered fractional Gaussian noise, provide a useful new stochastic model for wind speed data. A tempered difference forms the basis for numerical methods to solve tempered fractional diffusion equations, and it also provides a useful new correlation model in time series.

  14. Patient understanding of moles and skin cancer, and factors influencing presentation in primary care: a qualitative study

    Directory of Open Access Journals (Sweden)

    Walter Fiona M

    2010-08-01

    Full Text Available Abstract Background Melanoma incidence in the UK has doubled over two decades, yet there is conflicting evidence about factors which prompt or delay patients seeking advice. Aim: To explore patient understanding of pigmented skin lesions (moles and skin cancer, and factors which influence seeking help in primary care. Method Semi-structured interviews with forty MoleMate Trial participants, analysed using the theoretical framework of the Safer-Andersen model of Total Patient Delay. Results Patient understanding and awareness was influenced by personal, family and friends' experiences of moles, skin cancer and other cancers, knowledge of risk factors, and the lay media. The route to consulting was complex and often iterative. For lesions that people could see, detecting and appraising change was influenced by comparisons with a normal mole on themselves, a family member, friend or image. Inferring illness came about with recognition of changes (particularly size as serious, and associated 'internal' symptoms such as pain. For lesions that people could not see, family, friends and health professionals detected and appraised changes. Deciding to seek help was often prompted by another person or triggered by rapid or multiple changes in a mole. Three of four people subsequently diagnosed with melanoma did not seek help; instead, their GP opportunistically noticed the lesion. Conclusions Changing moles are often perceived as trivial and not signifying possible skin cancer. This study contributes to current national strategies to improve patient awareness and earlier diagnosis of cancer by highlighting factors that can trigger or act as barriers to seeking help. (ISRCTN79932379

  15. Evidência molecular da ocorrência de um fitoplasma associado ao lenho mole da macieira

    OpenAIRE

    Ribeiro,Luiz Fernando Caldeira; Bedendo,Ivan Paulo; Sanhueza,Rosa Maria Valdebenito

    2007-01-01

    O lenho mole da macieira é uma doença relevante em diversas partes do mundo. Sintomas típicos desta doença têm sido observados em pomares instalados em estados do sul do território brasileiro desde a década de oitenta. Enxertia tem revelado a natureza infecciosa da doença e a observação de corpúsculos filamentosos no floema tem evidenciado possível associação com fitoplasma. No presente trabalho plantas com sintomas de lenho mole foram coletadas em pomar comercial, visando demonstrar a presen...

  16. Prevalence and Factors Associated with Hydatidiform Mole among Patients Undergoing Uterine Evacuation at Mbarara Regional Referral Hospital

    Directory of Open Access Journals (Sweden)

    Olivier Mulisya

    2018-01-01

    Full Text Available Objective. We sought to determine the prevalence of and factors associated with hydatidiform molar gestations amongst patients undergoing uterine evacuation at Mbarara Regional Referral Hospital (MRRH, Mbarara, Uganda. Methods. This was a cross-sectional study carried out from November 2016 to February 2017. All patients admitted for uterine evacuation for nonviable pregnancy were included. The study registered 181 patients. Data were collected on sociodemographics, medical conditions, obstetrics, and gynecological factors. The evacuated tissue received a full gross and histopathologic examination. Cases of pathologically suspected complete hydatidiform mole were confirmed by p57 immunohistochemistry. Data were analyzed using STATA 13. Results. The prevalence of hydatidiform mole was 6.1% (11/181. All detected moles were complete hydatidiform moles, and there were no diagnosed partial hydatidiform moles. Clinical diagnosis of molar pregnancy was suspected in 13 patients, but only 69.2% (9/13 were confirmed as molar pregnancies histologically. Two cases were clinically unsuspected. Factors that had a significant relationship with complete hydatidiform mole included maternal age of 35 years and above (aOR 13.5; CI: 1.46–125.31; p=0.00, gestational age beyond the first trimester at the time of uterine evacuation (aOR 6.2; CI: 1.07–36.14; p=0.04, and history of previous abortion (aOR 4.3; CI: 1.00–18.57; p=0.05. Conclusion. The prevalence of complete hydatidiform mole was high at 6.1%. Associated risk factors included advanced maternal age (35 years and above, history of previous abortions, and gestational age beyond the first trimester at the time of evacuations. Recommendations. We recommend putting in place capacity to do routine histopathological examination of all products of conception especially those at high risk for a molar gestation either by clinical suspicion or by risk factors including advanced maternal age, advanced gestational

  17. Gis-approach for variability assessment of soil electric conductivity under pedoturbation activity of mole rat (Spalax microphthalmus

    Directory of Open Access Journals (Sweden)

    T. М. Konovalova

    2010-06-01

    Full Text Available The results of the investigation of the impact of the mole rat’s activity on soil electric conductivity have been presented. GIS-technology have been shown to be effective for assessment of the pedoturbation activity effect on the soil surface heterogeneity formation. Method of the one-dimension spatial coordinated array transformation into matrix form has been proposed for following multidimension statistic analysis application. The quantity estimation of the mole rats role in formation of the habitat nanorelief-level diversity has been obtained by means of indexes of the landscape complexity and diversity.

  18. Spatial variability of soil electrical conductivity under the mole rats (Spalax microphthalmus digging activity at the different scales

    Directory of Open Access Journals (Sweden)

    A. V. Zhukov

    2012-07-01

    Full Text Available The soil mounds emerged owing to the mole rats’ digging activity have been shown to be characterised by less electrical conductivity than surrounded soil. This effect is due to the changes of the mounds bulk’s density and moisture. The effect of the mole rats’ digging activity on the soil electrical conductivity has been found not to be restricted by the geometrical border of the mounds. The mounds are surrounded by 1–1.5 m halo of increased soil electrical conductivity. The halo size is increased with the aging of the mound and with the compacting of their aggregation.

  19. Whack-a-mole strategy for multifocal ground glass opacities of the lung.

    Science.gov (United States)

    Suzuki, Kenji

    2017-04-01

    Ground glass opacity (GGO) is a good prognostic indicator for lung cancer and is useful for physicians to predict prognosis. Due to recent advances in computed tomography (CT), the chance to encounter GGO is rapidly increasing in clinical practice. Based on the studies on radiological pathological correlation, GGO represents pathological lepidic growth and consolidation on CT represents pathologically invasive components. Thus, consolidation tumor ratio 0.5 or less means pathological less invasiveness for lung cancer. Not a few studies have shown that sublobar resection is equivalent to lobectomy for radiological early lung cancers. Additionally, observation of GGO is one of the options for physicians. Indication of surgical intervention remains unclear. Physician observing GGO in practice should know the natural history of GGO to reach an optimal treatment decision. For multifocal GGO lesions clinical management is surely challenging. Whack-a-mole strategy, which means sublobar resection for radiological invasive cancer is one of the most promising strategies for such lesions.

  20. Sarcomas de partes moles: experiência cirúrgica de cinco anos em hospital escola

    Directory of Open Access Journals (Sweden)

    Gabrielle Amaral Nunes

    2012-10-01

    Full Text Available INTRODUÇÃO Os sarcomas de partes moles compõem um grupo heterogêneo de neoplasias malignas com diferentes padrões morfológicos da linhagem mesenquimal. O Hospital de Clínicas de Porto Alegre (HCPA é um centro de referência para tratamento desta doença, interessando, por isso, o conhecimento de dados demográficos, clínicos, anátomo-patológicos e terapêuticos dos casos aqui tratados. OBJETIVO Estudar retrospectivamente os registros de pacientes operados por sarcomas de partes moles no HCPA nos últimos cinco anos e cotejar os resultados com os encontrados na literatura, como estadiamento, tipo histológico, localização e tratamento.  MÉTODOS Foram revisados os prontuários eletrônicos de pacientes com 18 ou mais anos de idade, que foram submetidos a tratamento cirúrgico de sarcoma de partes moles, no período entre 2006-2011. Os dados foram registrados em banco de dados no Microsoft Excel, no qual se coletaram informações referentes a idade, sexo, características histopatológicas, estadiamento, tipo de cirurgia, margens cirúrgicas, complicações cirúrgicas, tempo livre de doença, sobrevida e tratamentos complementares. RESULTADOS Os prontuários de 141 pacientes foram avaliados. Excluídos os casos com cirurgia em outra instituição e os que não foram tratados com cirurgia, 40 prontuários compuseram esta amostra. Os tipos histológicos mais frequentes foram histiocitoma fibroso maligno (27,5% e fibrossarcoma (15%, tumor desmoide (12,5%, leiomiossarcoma (10% e GIST (10%. Os locais mais acometidos foram os membros inferiores (40% e o abdome (30%. A maioria dos pacientes apresentava doença em estádio avançado (III no momento da cirurgia, principalmente devido ao grande tamanho do tumor (média de 12,2 cm e ao alto grau histológico (G3, encontrado em 50% dos pacientes. Cirurgias conservadoras de extremidades foram realizadas em 85% dos pacientes. Em 80% dos casos foi indicado tratamento complementar. A média do

  1. Comparative analysis of genome maintenance genes in naked mole rat, mouse, and human.

    Science.gov (United States)

    MacRae, Sheila L; Zhang, Quanwei; Lemetre, Christophe; Seim, Inge; Calder, Robert B; Hoeijmakers, Jan; Suh, Yousin; Gladyshev, Vadim N; Seluanov, Andrei; Gorbunova, Vera; Vijg, Jan; Zhang, Zhengdong D

    2015-04-01

    Genome maintenance (GM) is an essential defense system against aging and cancer, as both are characterized by increased genome instability. Here, we compared the copy number variation and mutation rate of 518 GM-associated genes in the naked mole rat (NMR), mouse, and human genomes. GM genes appeared to be strongly conserved, with copy number variation in only four genes. Interestingly, we found NMR to have a higher copy number of CEBPG, a regulator of DNA repair, and TINF2, a protector of telomere integrity. NMR, as well as human, was also found to have a lower rate of germline nucleotide substitution than the mouse. Together, the data suggest that the long-lived NMR, as well as human, has more robust GM than mouse and identifies new targets for the analysis of the exceptional longevity of the NMR. © 2015 The Authors. Aging Cell published by the Anatomical Society and John Wiley & Sons Ltd.

  2. Ultrastructural effects of ultraviolet C radiation on the stratum basale of mole rats epidermis

    Directory of Open Access Journals (Sweden)

    Mustafa Yel

    2014-10-01

    Full Text Available The ultrastructure of the epidermis of mole rats (Spalax leucodon was studied after irradiation with ultraviolet (UV light (λmax = 254 nm; 0.00147 J cm−2 s−1; for periods of 52, 112 and 168 h by using transmission electron microscope (TEM. After irradiation, Vacuolation in cytoplasm and mitochondria, and wrinkled nucleus were found in the stratum basal cells. Also, pathological aggregations of tonofilaments are formed in the desmosomes in these cells. These findings clearly demonstrated the harmful effects of ultraviolet C radiation on the stratum basale. The degree of pathological changes occurred depending on exposure time and radiation dosage applied.

  3. Lipid profile and serum characteristics of the blind subterranean mole rat, Spalax.

    Directory of Open Access Journals (Sweden)

    Nicola J Nasser

    Full Text Available BACKGROUND: Spalax (blind subterranean mole rat, is a mammal adapted to live in fluctuating oxygen levels, and can survive severe hypoxia and hypercapnia. The adaptive evolution of Spalax to underground life resulted in structural and molecular-genetic differences comparing to above-ground mammals. These differences include higher myocardial maximal oxygen consumption, increased lung diffusion capacity, increased blood vessels density, and unique expression patterns of cancer and angiogenesis related genes such as heparanase, vascular endothelial growth factor, and P53. METHODOLOGY/PRINCIPAL FINDINGS: Here we elucidate the main characteristics of Spalax lipid profile, as well as its main antioxidant and serum parameters. Compared to human, Spalax possesses lower total-cholesterol, low density lipoproteins (LDL and triglycerides levels, and higher levels of high density lipoproteins (HDL. Apolipoprotein A-I and apolipoprotein B-100 were significantly lower in Spalax compared to human. Paraoxonase (PON 1 arylesterase activity, was higher in Spalax compared to both human and mouse serum levels. Analysis of serum chemistry of Spalax revealed special features in this mammal. CONCLUSIONS/SIGNIFICANCE: Spalax possesses a unique lipid profile with high HDL and low LDL lipoproteins. The antioxidant serum content in the mole rat is higher than that of human and mouse. Serum C reactive protein (CRP levels are significantly lower in Spalax compared to that of human or mouse, reflecting low levels of inflammation. These differences between Spalax, human and mouse are due to several factors including the intensive activity life-style that Spalax pursue underground, dietary components, and evolutionary genetic adaptations. Unfolding the genetic basis of these differences will probably result in unique treatments for a variety of human diseases such as dyslipedemias, inflammation and cancer.

  4. EVALUATION OF VIRULENCE OF STEINERNEMA CARPOCAPSAE TO EUROPEAN MOLE CRICKET GRYLLOTALPA GRYLOTALPA L.

    Science.gov (United States)

    Stefanovska, T; Pisdlisnyuk, V

    2014-01-01

    Common European mole cricket (CEML) Grillotalpa grillotalpa L causes damage to field, vegetable crops, and small fruits growing at commercial plantations and nurseries. Chemical control if insecticides are used in poison bates, soil application or seedling/bulbs treatment is not environmentally friendly. Inundative and innoculative release of CTVL biocontrol agents, in particularly, Entomopathogenic nematode is a reliable alternative to chemical control. At the laboratory study the comparison of the ability of commercial strain (Nemastar) and local Ukrainian isolate of Steinernema carpocapsae in various concentrations to parasite in last instar nymph and adults of G. grillotalpa was investigated. Grillotalpa grillotalpa was found as a susceptible host for both commercial and local strains of S. carpocapsae. The life cycle of S. carpocapsae both strains in the adults of G. grillotapla with concentration 50 IJs per larva has been completed 12-15 days at t=25 C. Two generations of S. carpocapsae were able to develop in mole cricket for both strains. Two strains of S. carpocapsae nematode species tested were pathogenic to adults of G. grillotalpa. The mortalities of G. grillotapla last last instars' larva caused by S. carpocapsae were recorded in every concentration tested at least 20 to 150 IJs per larva. Mean larval mortality ranged from 48% to 95% depending upon nematode strain and rate of application. Larval mortality generally increased with increasing of nematode rates. It was significant for both S. carpocapsae strains (Ukr. Isolate F = 26 > 2,86) and commercial strain (Nemastar F = 102,95 > 2,86). Ukrainian local isolate caused a greater percentage of mortality of G. grillotapla adult than commercial strain of S. carpocapsae tested but interactions between nematode strains, application rates were not significant. This study presents new data on effect of S. carpocapsae isolated for Ukraine to key agricultural polyphagous pest G. grillotalpa susceptibility

  5. Effect of Temperature and Mole Ratio on the Synthesis Yield of Rhenium-Tetrofosmin

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    Widyastuti

    2015-08-01

    Full Text Available Technetium-99m (99mTc tetrofosmin is widely used in nuclear medicine as a diagnostic agent for myocardial perfusion and as a tumor imaging agent. As a parenteral preparation it requires an evaluation of its pharmacokinetics and stability in-vivo. Since 99mTc has a short half-life and is only available in very low concentrations, it is impossible to characterize its chemical properties and presence in the body. Due to this reason, only technetium-99 (T1/2 = 5 × 105 years, which is available in macro quantities, or natural rhenium can be used for this purpose. In this study rhenium-188 (188Re tetrofosmin will be synthesized and applied, because non-radioactive Re can be easily obtained. Synthesis and radiochemical purity analysis of carrier-added 188Re-tetrofosmin were carried out as a model to study the in-vivo stability of technetium-99m tetrofosmin. Rhenium-188 was used as a tracer to identify the formation of rhenium tetrofosmin. Rhenium gluconate was synthesized first prior to the formation of rhenium tetrofosmin. The quality of labeling for both rhenium gluconate and rhenium tetrofosmin was analyzed using paper- and thin-layer chromatography, respectively. Rhenium gluconate can be synthesized with high labeling yield within 1 hour, whereas rhenium tetrofosmin was synthesized both in room temperature and in an elevated temperature with various tetrofosmin-to-rhenium mole ratios.The results showed that heating at 95oC led to a higher yield of more than 90% within 30 minutes. Rhenium tetrofosmin could be produced in high radiochemical purity using an excess of tetrofosmin with mole ratio of 2000. It is concluded that rhenium tetrofosmin could be synthesized through the formation of rhenium gluconate, and a higher yield could be obtained in a shorter time by heating process.

  6. Swedish CDKN2A mutation carriers do not present the atypical mole syndrome phenotype.

    Science.gov (United States)

    Nielsen, Kari; Harbst, Katja; Måsbäck, Anna; Jönsson, Göran; Borg, Ake; Olsson, Håkan; Ingvar, Christian

    2010-08-01

    Phenotypic characteristics were examined in melanoma-prone southern Swedish CDKN2A (p16-113insArg/p14ARF-128insSer) mutation families, in relation to the CDKN2A genotype, nevi, clinically atypical nevi (CAN) and melanoma. Individuals from eight melanoma-prone families, with index patients carrying the CDKN2A mutation, were offered skin examinations and genotyping (CDKN2A and MC1R). Ninety-three individuals above 18 years of age participated; 29 invasive melanomas in 16 patients were recorded, all in the 38 verified CDKN2A mutation carriers. Median age at diagnosis was 36 years. Several MC1R variants were observed. A significant correlation to CAN (P=0.01) and red hair colour (P=0.02) could be confirmed in melanoma patients. A positive mutation status (CDKN2A) was correlated to one or more CAN (P=0.007) but neither to blue eyes, red hair colour, heavy freckling nor high number of nevi. For mutation carriers, median total naevus count was 24 and interquartile range was 12-47 (mean 31); whereas for the whole cohort, median total naevus count was 12 and interquartile range was 5-25 (mean 22). No participant fulfilled the atypical mole syndrome phenotype criteria. Melanomas were diagnosed only in mutation carriers, and melanoma diagnosis was statistically correlated to the presence of one or more CAN and red hair colour, supporting the possible synergistic effect of a MC1R mutation on increased risk of melanoma in patients with a CDKN2A mutation. Family history, with verified tumour diagnoses, remains an important clinical tool for finding mutation carriers for referral to clinical geneticists and simultaneous presence of CAN in probable mutation carriers might strengthen this indication. The atypical mole syndrome phenotype was, however, not verified in the studied families and total naevus counts were low.

  7. Ear Structures of the Naked Mole-Rat, Heterocephalus glaber, and Its Relatives (Rodentia: Bathyergidae.

    Directory of Open Access Journals (Sweden)

    Matthew J Mason

    Full Text Available Although increasingly popular as a laboratory species, very little is known about the peripheral auditory system of the naked mole-rat, Heterocephalus glaber. In this study, middle and inner ears of naked mole-rats of a range of ages were examined using micro-computed tomography and dissection. The ears of five other bathyergid species (Bathyergus suillus, Cryptomys hottentotus, Fukomys micklemi, Georychus capensis and Heliophobius argenteocinereus were examined for comparative purposes. The middle ears of bathyergids show features commonly found in other members of the Ctenohystrica rodent clade, including a fused malleus and incus, a synovial stapedio-vestibular articulation and the loss of the stapedius muscle. Heterocephalus deviates morphologically from the other bathyergids examined in that it has a more complex mastoid cavity structure, poorly-ossified processes of the malleus and incus, a 'columelliform' stapes and fewer cochlear turns. Bathyergids have semicircular canals with unusually wide diameters relative to their radii of curvature. How the lateral semicircular canal reaches the vestibule differs between species. Heterocephalus has much more limited high-frequency hearing than would be predicted from its small ear structures. The spongy bone forming its ossicular processes, the weak incudo-stapedial articulation, the columelliform stapes and (compared to other bathyergids reduced cochlear coiling are all potentially degenerate features which might reflect a lack of selective pressure on its peripheral auditory system. Substantial intraspecific differences were found in certain middle and inner ear structures, which might also result from relaxed selective pressures. However, such interpretations must be treated with caution in the absence of experimental evidence.

  8. Social condition and oxytocin neuron number in the hypothalamus of naked mole-rats (Heterocephalus glaber).

    Science.gov (United States)

    Mooney, S J; Holmes, M M

    2013-01-29

    The naked mole-rat is a subterranean colonial rodent. In each colony, which can grow to as many as 300 individuals, there is only one female and 1-3 males that are reproductive and socially dominant. The remaining animals are reproductively suppressed subordinates that contribute to colony survival through their cooperative behaviors. Oxytocin is a peptide hormone that has shown relatively widespread effects on prosocial behaviors in other species. We examined whether social status affects the number of oxytocin-immunoreactive neurons in the paraventricular nucleus and the supraoptic nucleus by comparing dominant breeding animals to subordinate non-breeding workers from intact colonies. We also examined these regions in subordinate animals that had been removed from their colony and paired with an opposite- or same-sex conspecific for 6 months. Stereological analyses indicated that subordinates had significantly more oxytocin neurons in the paraventricular nucleus than breeders. Animals in both opposite- and same-sex pairs showed a decreased oxytocin neuron number compared to subordinates suggesting that status differences may be due to social condition rather than the reproductive activity of the animal per se. The effects of social status appear to be region specific as no group differences were found for oxytocin neuron number in the supraoptic nucleus. Given that subordinate naked mole-rats are kept reproductively suppressed through antagonism by the queen, we speculate that status differences are due either to oxytocin's anxiolytic properties to combat the stress of this antagonism or to its ability to promote the prosocial behaviors of subordinates. Copyright © 2012 IBRO. Published by Elsevier Ltd. All rights reserved.

  9. Ear Structures of the Naked Mole-Rat, Heterocephalus glaber, and Its Relatives (Rodentia: Bathyergidae).

    Science.gov (United States)

    Mason, Matthew J; Cornwall, Hannah L; Smith, Ewan St J

    2016-01-01

    Although increasingly popular as a laboratory species, very little is known about the peripheral auditory system of the naked mole-rat, Heterocephalus glaber. In this study, middle and inner ears of naked mole-rats of a range of ages were examined using micro-computed tomography and dissection. The ears of five other bathyergid species (Bathyergus suillus, Cryptomys hottentotus, Fukomys micklemi, Georychus capensis and Heliophobius argenteocinereus) were examined for comparative purposes. The middle ears of bathyergids show features commonly found in other members of the Ctenohystrica rodent clade, including a fused malleus and incus, a synovial stapedio-vestibular articulation and the loss of the stapedius muscle. Heterocephalus deviates morphologically from the other bathyergids examined in that it has a more complex mastoid cavity structure, poorly-ossified processes of the malleus and incus, a 'columelliform' stapes and fewer cochlear turns. Bathyergids have semicircular canals with unusually wide diameters relative to their radii of curvature. How the lateral semicircular canal reaches the vestibule differs between species. Heterocephalus has much more limited high-frequency hearing than would be predicted from its small ear structures. The spongy bone forming its ossicular processes, the weak incudo-stapedial articulation, the columelliform stapes and (compared to other bathyergids) reduced cochlear coiling are all potentially degenerate features which might reflect a lack of selective pressure on its peripheral auditory system. Substantial intraspecific differences were found in certain middle and inner ear structures, which might also result from relaxed selective pressures. However, such interpretations must be treated with caution in the absence of experimental evidence.

  10. Peripheral administration of oxytocin increases social affiliation in the naked mole-rat (Heterocephalus glaber).

    Science.gov (United States)

    Mooney, Skyler J; Douglas, Natasha R; Holmes, Melissa M

    2014-04-01

    The neuropeptide oxytocin regulates a wide variety of social behaviors across diverse species. However, the types of behaviors that are influenced by this hormone are constrained by the species in question and the social organization that a particular species exhibits. Therefore, the present experiments investigated behaviors regulated by oxytocin in a eusocial mammalian species by using the naked mole-rat (Heterocephalus glaber). In Experiment 1, adult non-breeding mole-rats were given intraperitoneal injections of either oxytocin (1mg/kg or 10mg/kg) or saline on alternate days. Animals were then returned to their colony and behavior was recorded for minutes 15-30 post-injection. Both doses of oxytocin increased huddling behavior during this time period. In Experiment 2, animals received intraperitoneal injections of either oxytocin (1mg/kg), an oxytocin-receptor antagonist (0.1mg/kg), a cocktail of oxytocin and the antagonist, or saline across 4 testing days in a counterbalanced design. Animals were placed in either a 2-chamber arena with a familiar conspecific or in a small chamber with 1week old pups from their home colony and behaviors were recorded for minutes 15-30 post-injection. Oxytocin increased investigation of, and time spent in close proximity to, a familiar conspecific; these effects were blocked by the oxytocin antagonist. No effects were seen on pup-directed behavior. These data suggest that oxytocin is capable of modulating affiliative-like behavior in this eusocial species. Copyright © 2014 Elsevier Inc. All rights reserved.

  11. Anovulation in non-reproductive female Damaraland mole-rats (Cryptomys damarensis).

    Science.gov (United States)

    Molteno, A J; Bennett, N C

    2000-05-01

    Within colonies of Damaraland mole-rats (Cryptomys damarensis), anovulation in non-reproductive females is thought to play an important role in maintaining reproductive skew. Pituitary sensitivity and ovarian structure were examined in three groups of females that differed with respect to their social environment and breeding status to determine whether anovulation is due to inhibitory social cues or is merely the result of a lack of copulatory stimulation. The contribution of gonadal steroid negative feedback to neuroendocrine differences in the reproductive systems of the respective groups was also investigated. LH secretion after a 0.5 micrograms GnRH challenge in females that had been removed from the presence of the breeding individuals for at least 6 months (removed non-reproductive females) was significantly higher than in non-reproductive females in the colony, but significantly lower than in reproductive females. In both removed non-reproductive females and reproductive females, corpora lutea were observed in ovaries of seven of eight females, indicating that ovulation occurs spontaneously in subordinate females on removal from the breeding pair. Circulating progesterone concentrations in removed non-reproductive females were significantly higher than in non-reproductive females, indicating that circulating progesterone is not responsible for infertility in non-reproductive females. Indeed, after hystero-ovariectomy, reproductive females continued to show significantly greater GnRH-stimulated LH secretion than non-reproductive females. Thus, differential inhibition of gonadotrophin secretion in breeding and non-breeding females occurs independently of gonadal steroids. It is concluded that female Damaraland mole-rats are spontaneous ovulators and that anovulation results from inhibitory social cues within the colony, not a lack of copulatory stimulation. Since non-reproductive females are infertile, inhibition of the hypothalamo-pituitary-gonadal axis has

  12. TEMPERED FRACTIONAL CALCULUS

    OpenAIRE

    MEERSCHAERT, MARK M.; SABZIKAR, FARZAD; CHEN, JINGHUA

    2015-01-01

    Fractional derivatives and integrals are convolutions with a power law. Multiplying by an exponential factor leads to tempered fractional derivatives and integrals. Tempered fractional diffusion equations, where the usual second derivative in space is replaced by a tempered fractional derivative, govern the limits of random walk models with an exponentially tempered power law jump distribution. The limiting tempered stable probability densities exhibit semi-heavy tails, which are commonly obs...

  13. Fabrication of Densely Packed AlN Nanowires by a Chemical Conversion of Al2O3Nanowires Based on Porous Anodic Alumina Film

    Directory of Open Access Journals (Sweden)

    Wang Da-Jian

    2009-01-01

    Full Text Available Abstract Porous alumina film on aluminum with gel-like pore wall was prepared by a two-step anodization of aluminum, and the corresponding gel-like porous film was etched in diluted NaOH solution to produce alumina nanowires in the form of densely packed alignment. The resultant alumina nanowires were reacted with NH3and evaporated aluminum at an elevated temperature to be converted into densely packed aluminum nitride (AlN nanowires. The AlN nanowires have a diameter of 15–20 nm larger than that of the alumina nanowires due to the supplement of the additional evaporated aluminum. The results suggest that it might be possible to prepare other aluminum compound nanowires through similar process.

  14. Stabilization of Au Monatomic-High Islands on the (2 ×2 )-Nad Reconstructed Surface of Wurtzite AlN(0001)

    Science.gov (United States)

    Eydoux, Benoit; Baris, Bulent; Khoussa, Hassan; Guillermet, Olivier; Gauthier, Sébastien; Bouju, Xavier; Martrou, David

    2017-10-01

    Noncontact atomic force microscopy images show that gold grows on the (2 ×2 )-Nad reconstructed polar (0001) surface of AlN insulating films, in the form of large monatomic islands. High-resolution images and in situ reflection high-energy electron diffraction spectra reveal two moiré patterns from which an atomic model can be built. Density functional theory calculations confirm this model and give insight into the mechanisms that lead to the stabilization of the monolayer. Gold adsorption is accompanied, first, by a global vertical charge transfer from the AlN substrate that fulfills the electrostatic stability criterion for a polar material, and second, by lateral charge transfers that are driven by the local chemical properties of the (2 ×2 )-Nad reconstruction. These results present alternative strategies to grow metal electrodes onto nitride compounds with a better controlled interface, a crucial issue for applications.

  15. Effects of external surface charges on the enhanced piezoelectric potential of ZnO and AlN nanowires and nanotubes

    Directory of Open Access Journals (Sweden)

    Seong Min Kim

    2012-12-01

    Full Text Available We theoretically investigate external surface charge effects on piezoelectric potential of ZnO and AlN nanowires (NWs and nanotubes (NTs under uniform compression. The free carrier depletion caused by negative surface charges via surface functionalization on vertically compressed ZnO and AlN NWs/NTs is simulated using finite element calculation; this indicates the enhancement of piezoelectric potential is due to the free carriers (electrons being fully depleted at the critical surface charge density. Numerical simulations reveal that full coverage of surface charges surrounding the NTs increases the piezoelectric output potential exponentially within a relatively smaller range of charge density compared to the case of NWs for a typical donor concentration (∼1017 cm−3. The model can be used to design functional high-power semiconducting piezoelectric nanogenerators.

  16. Control of two-dimensional growth of AlN and high Al-content AlGaN-based MQWs for deep-UV LEDs

    Directory of Open Access Journals (Sweden)

    Weihuang Yang

    2013-05-01

    Full Text Available Dense and atomically flat AlN film with root-mean-square roughness value of 0.32 nm was grown on sapphire substrate at a relatively lower temperature by using a three-step epitaxy technique. On the basis of this AlN template, AlGaN-based multiple quantum wells (MQWs with atomically flat hetero-interfaces were epitaxially grown to suppress nonradiative recombination by introducing In as a surfactant during simultaneous source supply. As a result, single intense- and narrow-peaked photoluminescence was obtained from the MQWs. Finally, the deep ultraviolet light emitting diodes with well-behaved I-V characteristic and strong electroluminescence in the range of 256–312 nm were fabricated successfully.

  17. fractional differential equations

    Indian Academy of Sciences (India)

    We apply this method for solving space–time fractional Cahn--Allen equation and space--time fractional Klein–Gordon equation. The fractional derivatives are described in the sense of modified Riemann--Lioville. As a result of some exact solution in the form of hyperbolic, trigonometric and rational solutions are deduced.

  18. Unfolding Fraction Multiplication

    Science.gov (United States)

    Wyberg, Terry; Whitney, Stephanie R.; Cramer, Kathleen A.; Monson, Debra S.; Leavitt, Seth

    2011-01-01

    Students often have difficulty understanding fractions, in general, and understanding how to multiply fractions, in particular. To move past this potential problem area, students need to develop a deeper understanding of multiplication and connect the ideas to fractions. In this article, the authors share their insights into teaching fraction…

  19. A comparative study on magnetic properties of Mo doped AlN, GaN and InN monolayers from first-principles

    Science.gov (United States)

    Xiao, Gang; Wang, Ling-Ling; Rong, Qing-Yan; Xu, Hai-Qing; Xiao, Wen-Zhi

    2017-11-01

    First-principles calculations are performed to comparatively study the structural, electronic structures and magnetic properties of Mo doped AlN, GaN and InN monolayers (MLs). After Mo atom doping, the semiconducting GaN and InN MLs transform to metal, while the AlN ML keeps semiconducting with a reduced gap. Total magnetic moments of 1.0 and 0.54 μB, which mainly arising from the localized Mo 4d states, are induced by doping in AlN and InN MLs, respectively, while the doped GaN ML is still nonmagnetic. Nevertheless, the excessive localization and strongly ionic character of the Mo-4d states in AlN ML directly impedes the magnetic coupling, leading to a paramagnetic ground states. A similar case is observed in Mo atoms doped InN ML. The firm N-Mo interaction prevent the impurity states permeating out the range of N-Mo pair, resulting in a quick vanishing of ferromagnetic coupling as the distance between two Mo atoms increasing. All configurations of Mo atoms doped GaN ML in this paper are room temperature ferromagnetic. Spin polarized itinerant electrons mediate the magnetic interaction between two Mo atoms. Increasing the Mo concentration may stabilize the FM state and produce a higher Curie temperature. Our calculations show that GaN nanosheets with Mo atoms doped may be a nice candidate for future spintronic devices. And we conclude that a appropriate magnitude of localization (or delocalization) is what the key point to produce room temperature ferromagnetism from this comparative study.

  20. Vocalisations of the silvery mole-rat: comparasion of vocal repertoires in subterrane an rodents with different socials systems

    Czech Academy of Sciences Publication Activity Database

    Knotková, E.; Veitl, S.; Šumbera, R.; Sedláček, František; Burda, H.

    2009-01-01

    Roč. 18, č. 3 (2009), s. 241-257 ISSN 0952-4622 Institutional research plan: CEZ:AV0Z60870520 Keywords : silvery mole-rat * bathyergidae * vocal communication Subject RIV: EG - Zoology Impact factor: 1.050, year: 2009

  1. A modified mole cricket lure and description of Scapteriscus borellii (Orthoptera: Gryllotalpidae) range expansion and calling song in California.

    Science.gov (United States)

    Dillman, Adler R; Cronin, Christopher J; Tang, Joseph; Gray, David A; Sternberg, Paul W

    2014-02-01

    Invasive mole cricket species in the genus Scapteriscus have become significant agricultural pests and are continuing to expand their range in North America. Though largely subterranean, adults of some species, such as Scapteriscus borellii Giglio-Tos 1894, are capable of long dispersive flights and phonotaxis to male calling songs to find suitable habitats and mates. Mole crickets in the genus Scapteriscus are known to be attracted to and can be caught by audio lure traps that broadcast synthesized or recorded calling songs. We report improvements in the design and production of electronic controllers for the automation of semipermanent mole cricket trap lures as well as highly portable audio trap collection designs. Using these improved audio lure traps, we collected the first reported individuals of the pest mole cricket S. borellii in California. We describe several characteristic features of the calling song of the California population including that the pulse rate is a function of soil temperature, similar to Florida populations of S. borellii. Further, we show that other calling song characteristics (carrier frequency, intensity, and pulse rate) are significantly different between the populations.

  2. Clinical utility of hyperglycosylated hCG in serum taken before hydatidiform mole evacuation to predict persistent trophoblastic disease.

    NARCIS (Netherlands)

    Duc, H.N.; Trommel, N.E. van; Sweep, C.G.J.; Massuger, L.F.A.G.; Thomas, C.M.G.

    2006-01-01

    OBJECTIVE: Human chorionic gonadotropin (hCG) is widely used in the management of hydatidiform mole and persistent trophoblastic disease (PTD). Studies on hyperglycosylated human chorionic gonadotropin (invasive trophoblast antigen, ITA) in PTD are limited. In serum samples taken before evacuation

  3. Functional neurokinin and NMDA receptor activity in an animal naturally lacking substance P: the naked mole-rat.

    Directory of Open Access Journals (Sweden)

    Antje Brand

    Full Text Available Naked mole-rats are extremely unusual among mammals in that their cutaneous C-fibers lack the neuropeptide Substance P (SP. In other mammals, SP plays an important role in nociception: it is released from C-fibers onto spinal neurons where it facilitates NMDA receptor activity and causes sensitization that can last for minutes, hours or days. In the present study, we tested the effects of intrathecal application of: 1 SP, 2 an SP antagonist (GR-82334, and 3 an NMDA antagonist (APV on heat-evoked foot withdrawal. In the naked mole-rat, at a high enough concentration, application of SP caused a large, immediate, and long-lasting sensitization of foot withdrawal latency that was transiently reversed by application of either antagonist. However, neither SP nor NMDA antagonists had an effect when administered alone to naïve animals. In contrast, both antagonists induced an increase in basal withdrawal latency in mice. These results indicate that spinal neurons in naked mole-rats have functional SP and NMDA receptors, but that these receptors do not participate in heat-evoked foot withdrawal unless SP is experimentally introduced. We propose that the natural lack of SP in naked mole-rat C-fibers may have resulted during adaptation to living in a chronically high carbon dioxide, high ammonia environment that, in other mammals, would stimulate C-fibers and evoke nocifensive behavior.

  4. Four Cases of Spontaneous Neoplasia in the Naked Mole-Rat (Heterocephalus glaber), A Putative Cancer-Resistant Species.

    Science.gov (United States)

    Taylor, Kyle R; Milone, Nicholas A; Rodriguez, Carlos E

    2017-01-01

    The naked mole-rat (Heterocephalus glaber) is widely acclaimed to be cancer-resistant and of considerable research interest based on a paucity of reports of neoplasia in this species. We have, however, encountered four spontaneous cases of neoplasia and one presumptive case of neoplasia through routine necropsy and biopsy of individuals in a zoo collection of nonhybrid naked mole-rats bred from a single pair. One case each of metastasizing hepatocellular carcinoma, nephroblastoma (Wilms' tumor), and multicentric lymphosarcoma, as well as presumptive esophageal adenocarcinoma (Barrett's esophagus-like) was identified postmortem among 37 nonautolyzed necropsy submissions of naked mole-rats over 1-year-old that were submitted for necropsy between 1998 and August 2015. One incidental case of cutaneous hemangioma was also identified antemortem by skin biopsy from one naked mole-rat examined for trauma. © The Author 2016. Published by Oxford University Press on behalf of The Gerontological Society of America. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

  5. Functional neurokinin and NMDA receptor activity in an animal naturally lacking substance P: the naked mole-rat.

    Science.gov (United States)

    Brand, Antje; Smith, Ewan St J; Lewin, Gary R; Park, Thomas J

    2010-12-21

    Naked mole-rats are extremely unusual among mammals in that their cutaneous C-fibers lack the neuropeptide Substance P (SP). In other mammals, SP plays an important role in nociception: it is released from C-fibers onto spinal neurons where it facilitates NMDA receptor activity and causes sensitization that can last for minutes, hours or days. In the present study, we tested the effects of intrathecal application of: 1) SP, 2) an SP antagonist (GR-82334), and 3) an NMDA antagonist (APV) on heat-evoked foot withdrawal. In the naked mole-rat, at a high enough concentration, application of SP caused a large, immediate, and long-lasting sensitization of foot withdrawal latency that was transiently reversed by application of either antagonist. However, neither SP nor NMDA antagonists had an effect when administered alone to naïve animals. In contrast, both antagonists induced an increase in basal withdrawal latency in mice. These results indicate that spinal neurons in naked mole-rats have functional SP and NMDA receptors, but that these receptors do not participate in heat-evoked foot withdrawal unless SP is experimentally introduced. We propose that the natural lack of SP in naked mole-rat C-fibers may have resulted during adaptation to living in a chronically high carbon dioxide, high ammonia environment that, in other mammals, would stimulate C-fibers and evoke nocifensive behavior.

  6. Influence of substrate biasing on the growth of c-axis oriented AlN thin films by RF reactive sputtering in pure nitrogen

    Energy Technology Data Exchange (ETDEWEB)

    Monteagudo-Lerma, L.; Naranjo, F.B.; Gonzalez-Herraez, M. [Departamento de Electronica, Escuela Politecnica, Universidad de Alcala, Campus Universitario, 28871 Alcala de Henares (Spain); Fernandez, S. [Departamento de Energias Renovables, Energia Solar Fotovoltaica, Centro de Investigaciones Energeticas, Medioambientales y Tecnologicas (CIEMAT), Avda. Complutense 22, 28040 Madrid (Spain)

    2012-03-15

    We report on the investigation of the influence of deposition conditions on structural, morphological and optical properties of AlN thin films deposited on sapphire (Al{sub 2}O{sub 3}) substrates by radio-frequency (RF) reactive sputtering. The deposition parameters studied are RF power, substrate temperature and substrate bias, while using pure nitrogen as reactive gas. The effect of such deposition parameters on AlN film properties are analyzed by different characterization methods as high resolution X-ray diffraction (HRXRD), field emission scanning electron microscopy (FESEM) and linear optical transmission. AlN thin films with a full-width at half-maximum (FWHM) of the rocking curve obtained for the (0002) diffraction peak of 1.2 are achieved under optimized conditions. The time resolved evolution of the self and externally-induced biasing of the substrate during deposition process is monitored and analyzed in terms of the rate of atomic species incorporation into the layer. The bias-induced change of the atomic incorporation leads to an enhancement in the structural quality of the layer and an increase of the deposition rate. (copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  7. The effect of ammonia flow in the AlN spacer on the electrical properties of InAlN/AlN/GaN HEMT structures

    International Nuclear Information System (INIS)

    Gamarra, Piero; Lacam, Cedric; Magis, Michelle; Tordjman, Maurice; Di Forte Poisson, Marie-Antoinette

    2012-01-01

    During the past few years it has been reported that a thin AlN spacer of few nanometers needs to be inserted in InAlN/GaN high electron mobility transistors (HEMTs) to obtain high 2DEG carrier mobility. This work presents a systematic study of the effects of varying the ammonia flow in the AlN spacer of InAlN/AlN/GaN HEMTs grown by low pressure metalorganic vapour phase epitaxy (LP-MOVPE). The strain state, the surface roughness and the growth rate of AlN were found to be dependent on the V/III ratio. In addition the ammonia flow in the interlayer has a strong impact on the structural properties of the subsequent InAlN barrier layer and on the electrical properties of the structure. A sheet resistance as low as 327 Ω/□ with a sheet carrier density of 1.5 x 10 13 cm -2 has been obtained at room temperature. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  8. The effect of ammonia flow in the AlN spacer on the electrical properties of InAlN/AlN/GaN HEMT structures

    Energy Technology Data Exchange (ETDEWEB)

    Gamarra, Piero; Lacam, Cedric; Magis, Michelle; Tordjman, Maurice; Di Forte Poisson, Marie-Antoinette [III-V Lab., Marcussis (France)

    2012-01-15

    During the past few years it has been reported that a thin AlN spacer of few nanometers needs to be inserted in InAlN/GaN high electron mobility transistors (HEMTs) to obtain high 2DEG carrier mobility. This work presents a systematic study of the effects of varying the ammonia flow in the AlN spacer of InAlN/AlN/GaN HEMTs grown by low pressure metalorganic vapour phase epitaxy (LP-MOVPE). The strain state, the surface roughness and the growth rate of AlN were found to be dependent on the V/III ratio. In addition the ammonia flow in the interlayer has a strong impact on the structural properties of the subsequent InAlN barrier layer and on the electrical properties of the structure.istance as low as 327 {omega}/{open_square} with a sheet carrier density of 1.5 x 10{sup 13} cm{sup -2} has been obtained at room temperature. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  9. Growth kinetics of AlN and GaN films grown by molecular beam epitaxy on R-plane sapphire substrates

    International Nuclear Information System (INIS)

    Chandrasekaran, R.; Moustakas, T. D.; Ozcan, A. S.; Ludwig, K. F.; Zhou, L.; Smith, David J.

    2010-01-01

    This paper reports the growth by molecular beam epitaxy of AlN and GaN thin films on R-plane sapphire substrates. Contrary to previous findings that GaN grows with its (1120) A-plane parallel to the (1102) R-plane of sapphire, our results indicate that the crystallographic orientation of the III-nitride films is strongly dependent on the kinetic conditions of growth for the GaN or AlN buffer layers. Thus, group III-rich conditions for growth of either GaN or AlN buffers result in nitride films having (1120) planes parallel to the sapphire surface, and basal-plane stacking faults parallel to the growth direction. The growth of these buffers under N-rich conditions instead leads to nitride films with (1126) planes parallel to the sapphire surface, with inclined c-plane stacking faults that often terminate threading dislocations. Moreover, electron microscope observations indicate that slight miscut (∼0.5 deg. ) of the R-plane sapphire substrate almost completely suppresses the formation of twinning defects in the (1126) GaN films.

  10. Fractional smith chart theory

    KAUST Repository

    Shamim, Atif

    2011-03-01

    For the first time, a generalized Smith chart is introduced here to represent fractional order circuit elements. It is shown that the standard Smith chart is a special case of the generalized fractional order Smith chart. With illustrations drawn for both the conventional integer based lumped elements and the fractional elements, a graphical technique supported by the analytical method is presented to plot impedances on the fractional Smith chart. The concept is then applied towards impedance matching networks, where the fractional approach proves to be much more versatile and results in a single element matching network for a complex load as compared to the two elements in the conventional approach. © 2010 IEEE.

  11. Photic induction of Fos in the suprachiasmatic nucleus of African mole-rats: responses to increasing irradiance.

    Science.gov (United States)

    Oosthuizen, Maria K; Bennett, Nigel C; Cooper, Howard M

    2010-09-01

    African mole-rats (family Bathyergidae) are strictly subterranean rodent species that are rarely exposed to environmental light. Morphological and physiological adaptations to the underground environment include a severely reduced eye size and regressed visual system. Responses of the circadian system to light, however, appear to be intact, since mole-rats are able to entrain their circadian activity rhythms to the light-dark cycle and light induces Fos expression in the suprachiasmatic nucleus (SCN). Social organization varies from solitary species to highly elaborated eusocial structures, characterized by a distinct division of labor and in which one reproductive female regulates the behavior and reproductive physiology of other individuals in the colony. The authors studied light-induced Fos expression in the SCN to increasing light intensities in four mole-rat species, ranging from strictly solitary to highly social. In the solitary Cape mole-rat, light induces significant Fos expression in the SCN, and the number of Fos-immunopositive cells increases with increasing light intensity. In contrast, Fos induction in the SCN of social species was slightly greater than, but not statistically different from, the dark-control animals as is typical of most rodents. One species showed a trend for an increase in expression with increased light, whereas a second species showed no trend in expression. In the naked mole-rat, Fos expression appeared higher in the dark-controls than in the animals exposed to light, although the differences in Fos expression were not significant. These results suggest a gradient in the sensitivity of the circadian system to light in mole-rats, with a higher percentage of individuals that are unresponsive to light in correlation with the degree of sociality. In highly social species, such as the naked mole-rat that live in a relatively stable subterranean milieu in terms of food availability, temperature, constant darkness, and devoid of 24-h

  12. Fractional factorial plans

    CERN Document Server

    Dey, Aloke

    2009-01-01

    A one-stop reference to fractional factorials and related orthogonal arrays.Presenting one of the most dynamic areas of statistical research, this book offers a systematic, rigorous, and up-to-date treatment of fractional factorial designs and related combinatorial mathematics. Leading statisticians Aloke Dey and Rahul Mukerjee consolidate vast amounts of material from the professional literature--expertly weaving fractional replication, orthogonal arrays, and optimality aspects. They develop the basic theory of fractional factorials using the calculus of factorial arrangements, thereby providing a unified approach to the study of fractional factorial plans. An indispensable guide for statisticians in research and industry as well as for graduate students, Fractional Factorial Plans features: * Construction procedures of symmetric and asymmetric orthogonal arrays. * Many up-to-date research results on nonexistence. * A chapter on optimal fractional factorials not based on orthogonal arrays. * Trend-free plans...

  13. Fractional Dynamics and Control

    CERN Document Server

    Machado, José; Luo, Albert

    2012-01-01

    Fractional Dynamics and Control provides a comprehensive overview of recent advances in the areas of nonlinear dynamics, vibration and control with analytical, numerical, and experimental results. This book provides an overview of recent discoveries in fractional control, delves into fractional variational principles and differential equations, and applies advanced techniques in fractional calculus to solving complicated mathematical and physical problems.Finally, this book also discusses the role that fractional order modeling can play in complex systems for engineering and science. Discusses how fractional dynamics and control can be used to solve nonlinear science and complexity issues Shows how fractional differential equations and models can be used to solve turbulence and wave equations in mechanics and gravity theories and Schrodinger’s equation  Presents factional relaxation modeling of dielectric materials and wave equations for dielectrics  Develops new methods for control and synchronization of...

  14. Expression of acid-sensing ion channels and selection of reference genes in mouse and naked mole rat.

    Science.gov (United States)

    Schuhmacher, Laura-Nadine; Smith, Ewan St John

    2016-12-13

    Acid-sensing ion channels (ASICs) are a family of ion channels comprised of six subunits encoded by four genes and they are expressed throughout the peripheral and central nervous systems. ASICs have been implicated in a wide range of physiological and pathophysiological processes: pain, breathing, synaptic plasticity and excitotoxicity. Unlike mice and humans, naked mole-rats do not perceive acid as a noxious stimulus, even though their sensory neurons express functional ASICs, likely an adaptation to living in a hypercapnic subterranean environment. Previous studies of ASIC expression in the mammalian nervous system have often not examined all subunits, or have failed to adequately quantify expression between tissues; to date there has been no attempt to determine ASIC expression in the central nervous system of the naked mole-rat. Here we perform a geNorm study to identify reliable housekeeping genes in both mouse and naked mole-rat and then use quantitative real-time PCR to estimate the relative amounts of ASIC transcripts in different tissues of both species. We identify RPL13A (ribosomal protein L13A) and CANX (calnexin), and β-ACTIN and EIF4A (eukaryotic initiation factor 4a) as being the most stably expressed housekeeping genes in mouse and naked mole-rat, respectively. In both species, ASIC3 was most highly expressed in dorsal root ganglia (DRG), and ASIC1a, ASIC2b and ASIC3 were more highly expressed across all brain regions compared to the other subunits. We also show that ASIC4, a proton-insensitive subunit of relatively unknown function, was highly expressed in all mouse tissues apart from DRG and hippocampus, but was by contrast the lowliest expressed ASIC in all naked mole-rat tissues.

  15. Electrical properties of GaAs metal–oxide–semiconductor structure comprising Al2O3 gate oxide and AlN passivation layer fabricated in situ using a metal–organic vapor deposition/atomic layer deposition hybrid system

    Directory of Open Access Journals (Sweden)

    Takeshi Aoki

    2015-08-01

    Full Text Available This paper presents a compressive study on the fabrication and optimization of GaAs metal–oxide–semiconductor (MOS structures comprising a Al2O3 gate oxide, deposited via atomic layer deposition (ALD, with an AlN interfacial passivation layer prepared in situ via metal–organic chemical vapor deposition (MOCVD. The established protocol afforded self-limiting growth of Al2O3 in the atmospheric MOCVD reactor. Consequently, this enabled successive growth of MOCVD-formed AlN and ALD-formed Al2O3 layers on the GaAs substrate. The effects of AlN thickness, post-deposition anneal (PDA conditions, and crystal orientation of the GaAs substrate on the electrical properties of the resulting MOS capacitors were investigated. Thin AlN passivation layers afforded incorporation of optimum amounts of nitrogen, leading to good capacitance–voltage (C–V characteristics with reduced frequency dispersion. In contrast, excessively thick AlN passivation layers degraded the interface, thereby increasing the interfacial density of states (Dit near the midgap and reducing the conduction band offset. To further improve the interface with the thin AlN passivation layers, the PDA conditions were optimized. Using wet nitrogen at 600 °C was effective to reduce Dit to below 2 × 1012 cm−2 eV−1. Using a (111A substrate was also effective in reducing the frequency dispersion of accumulation capacitance, thus suggesting the suppression of traps in GaAs located near the dielectric/GaAs interface. The current findings suggest that using an atmosphere ALD process with in situ AlN passivation using the current MOCVD system could be an efficient solution to improving GaAs MOS interfaces.

  16. Electrical properties of GaAs metal-oxide-semiconductor structure comprising Al2O3 gate oxide and AlN passivation layer fabricated in situ using a metal-organic vapor deposition/atomic layer deposition hybrid system

    Science.gov (United States)

    Aoki, Takeshi; Fukuhara, Noboru; Osada, Takenori; Sazawa, Hiroyuki; Hata, Masahiko; Inoue, Takayuki

    2015-08-01

    This paper presents a compressive study on the fabrication and optimization of GaAs metal-oxide-semiconductor (MOS) structures comprising a Al2O3 gate oxide, deposited via atomic layer deposition (ALD), with an AlN interfacial passivation layer prepared in situ via metal-organic chemical vapor deposition (MOCVD). The established protocol afforded self-limiting growth of Al2O3 in the atmospheric MOCVD reactor. Consequently, this enabled successive growth of MOCVD-formed AlN and ALD-formed Al2O3 layers on the GaAs substrate. The effects of AlN thickness, post-deposition anneal (PDA) conditions, and crystal orientation of the GaAs substrate on the electrical properties of the resulting MOS capacitors were investigated. Thin AlN passivation layers afforded incorporation of optimum amounts of nitrogen, leading to good capacitance-voltage (C-V) characteristics with reduced frequency dispersion. In contrast, excessively thick AlN passivation layers degraded the interface, thereby increasing the interfacial density of states (Dit) near the midgap and reducing the conduction band offset. To further improve the interface with the thin AlN passivation layers, the PDA conditions were optimized. Using wet nitrogen at 600 °C was effective to reduce Dit to below 2 × 1012 cm-2 eV-1. Using a (111)A substrate was also effective in reducing the frequency dispersion of accumulation capacitance, thus suggesting the suppression of traps in GaAs located near the dielectric/GaAs interface. The current findings suggest that using an atmosphere ALD process with in situ AlN passivation using the current MOCVD system could be an efficient solution to improving GaAs MOS interfaces.

  17. Protocol for the MoleMate™ UK Trial: a randomised controlled trial of the MoleMate system in the management of pigmented skin lesions in primary care [ISRCTN 79932379

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    Wilson Edward CF

    2010-05-01

    Full Text Available Abstract Background Suspicious pigmented lesions are a common presenting problem in general practice consultations; while the majority are benign a small minority are melanomas. Differentiating melanomas from other pigmented lesions in primary care is challenging: currently, 95% of all lesions referred to a UK specialist are benign. The MoleMate system is a new diagnostic aid, incorporating a hand-held SIAscopy scanner with a primary care diagnostic algorithm. This trial tests the hypothesis that adding the MoleMate system to current best primary care practice will increase the proportion of appropriate referrals of suspicious pigmented lesions to secondary care compared with current best practice alone. Methods/design The MoleMate UK Trial is a primary care based multi-centre randomised controlled trial, with randomisation at patient level using a validated block randomisation method for two age groups (45 years and under; 46 years and over. We aim to recruit adult patients seen in general practice with a pigmented skin lesion that cannot immediately be diagnosed as benign and the patient reassured. The trial has a 'two parallel groups' design, comparing 'best practice' with 'best practice' plus the MoleMate system in the intervention group. The primary outcome is the positive predictive value (PPV of referral defined as the proportion of referred lesions seen by secondary care experts that are considered 'clinically significant' (i.e. biopsied or monitored. Secondary outcomes include: the sensitivity, specificity and negative predictive value (NPV of the decision not to refer; clinical outcomes (melanoma thickness, 5 year melanoma incidence and mortality; clinician outcomes (Index of Suspicion, confidence, learning effects; patient outcomes (satisfaction, general and cancer-specific worry, and cost-utility. Discussion The MoleMate UK Trial tests a new technology designed to improve the management of suspicious pigmented lesions in primary care

  18. Intense Red Catho- and Photoluminescence from 200 nm Thick Samarium Doped Amorphous AlN Thin Films

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    Ali Tariq

    2009-01-01

    Full Text Available Abstract Samarium (Sm doped aluminum nitride (AlN thin films are deposited on silicon (100 substrates at 77 K by rf magnetron sputtering method. Thick films of 200 nm are grown at 100–200 watts RF power and 5–8 m Torr nitrogen, using a metal target of Al with Sm. X-ray diffraction results show that films are amorphous. Cathodoluminescence (CL studies are performed and four peaks are observed in Sm at 564, 600, 648, and 707 nm as a result of4G5/2 → 6H5/2,4G5/2 → 6H7/2,4G5/2 → 6H9/2, and4G5/2 → 6H11/2transitions. Photoluminescence (PL provides dominant peaks at 600 and 707 nm while CL gives the intense peaks at 600 nm and 648 nm, respectively. Films are thermally activated at 1,200 K for half an hour in a nitrogen atmosphere. Thermal activation enhances the intensity of luminescence.

  19. Texture of the nano-crystalline AlN thin films and the growth conditions in DC magnetron sputtering

    Directory of Open Access Journals (Sweden)

    Shakil Khan

    2015-08-01

    Full Text Available DC reactive magnetron sputtering technique has been used for the preparation of AlN thin films. The deposition temperature and the flow ratio of N2/Ar were varied and subsequent dependency of the films crystallites orientation/texture has been addressed. In general, deposited films were found hexagonal polycrystalline with a (002 preferred orientation. The X-ray diffraction (XRD data revealed that the film crystallinity improves, with the increase of substrate temperature from 300 °C to 500 °C. The dropped in full width half maximum (FWHM of the XRD rocking curve value further confirmed it. However, increasing substrate temperature above 500 °C or reducing the nitrogen condition (from 60 to 30% in the environment induced the growth of crystallites with (102 and (103 orientations. The rise of rocking curve FWHM for the corresponding conditions depicted that the films texture quality deteriorated. A further confirmation of the variation in film texture/orentation with the growth conditions has been obtained from the variation in FWHM values of a dominant E1 (TO mode in the Fourier transform infrared (FTIR spectra and the E2 (high mode in Raman spectra. We have correlated the columnar structure in AFM surface analyses with the (002 or c-axis orientation as well. Spectroscopic ellipsometry of the samples have shown a higher refractive index at 500 °C growth temperature.

  20. Intense Red Catho- and Photoluminescence from 200 nm Thick Samarium Doped Amorphous AlN Thin Films.

    Science.gov (United States)

    Maqbool, Muhammad; Ali, Tariq

    2009-04-25

    Samarium (Sm) doped aluminum nitride (AlN) thin films are deposited on silicon (100) substrates at 77 K by rf magnetron sputtering method. Thick films of 200 nm are grown at 100-200 watts RF power and 5-8 m Torr nitrogen, using a metal target of Al with Sm. X-ray diffraction results show that films are amorphous. Cathodoluminescence (CL) studies are performed and four peaks are observed in Sm at 564, 600, 648, and 707 nm as a result of (4)G(5/2) --> (6)H(5/2), (4)G(5/2) --> (6)H(7/2), (4)G(5/2) --> (6)H(9/2), and (4)G(5/2) --> (6)H(11/2) transitions. Photoluminescence (PL) provides dominant peaks at 600 and 707 nm while CL gives the intense peaks at 600 nm and 648 nm, respectively. Films are thermally activated at 1,200 K for half an hour in a nitrogen atmosphere. Thermal activation enhances the intensity of luminescence.

  1. Determination of electron penetration depth and stopping power of amorphous AlN using luminescence of Tm and Ho ions

    Science.gov (United States)

    Maqbool, Muhammad; Kordesch, Martin

    2006-03-01

    Electron penetration depth and stopping power of amorphous AlN is determined using luminescence of Tm^+3 and Ho^+3 ions. Thin film bilayers of AlN:Ho and AlN:Tm are deposited on flat Silicon substrates by RF Magnetron sputtering at liquid nitrogen temperatures. In making a bilayer, 15.3 nm thick AlN:Ho film is first deposited on a flat Si(111) substrate of 2x2 cm^2 surface area. On the top of this AlN:Ho film 37.8 nm thick AlN:Tm film is deposited to make it a bilayer. Electron beam of different energies, obtained from electron gun of the CL apparatus, is allowed to penetrate in the AlN:Tm/AlN:Ho bilayer film. Blue emission from Tm^+3 as a result from ^1D2 -> ^3F4 transition and green emission from Ho^+3 as a result from ^5S2 -> ^5I8 transition were used to track the electron beam penetrating in the bilayer. Energy of the beam just crossing 37.8 nm AlN:Tm film is recorded to obtain the stopping power experimentally. Experimental results are compared to the theoretical value using the established mathematical equations for stopping power. A percent deviation of 6.6% is found in the experimental and theoretical results.

  2. Intense Red Catho- and Photoluminescence from 200 nm Thick Samarium Doped Amorphous AlN Thin Films

    Science.gov (United States)

    Maqbool, Muhammad; Ali, Tariq

    2009-07-01

    Samarium (Sm) doped aluminum nitride (AlN) thin films are deposited on silicon (100) substrates at 77 K by rf magnetron sputtering method. Thick films of 200 nm are grown at 100-200 watts RF power and 5-8 m Torr nitrogen, using a metal target of Al with Sm. X-ray diffraction results show that films are amorphous. Cathodoluminescence (CL) studies are performed and four peaks are observed in Sm at 564, 600, 648, and 707 nm as a result of 4G5/2 → 6H5/2, 4G5/2 → 6H7/2, 4G5/2 → 6H9/2, and 4G5/2 → 6H11/2 transitions. Photoluminescence (PL) provides dominant peaks at 600 and 707 nm while CL gives the intense peaks at 600 nm and 648 nm, respectively. Films are thermally activated at 1,200 K for half an hour in a nitrogen atmosphere. Thermal activation enhances the intensity of luminescence.

  3. High internal quantum efficiency in AlGaN multiple quantum wells grown on bulk AlN substrates

    Energy Technology Data Exchange (ETDEWEB)

    Bryan, Zachary, E-mail: zabryan@ncsu.edu; Bryan, Isaac; Sitar, Zlatko; Collazo, Ramón [Department of Materials Science and Engineering, North Carolina State University, Raleigh, North Carolina 27695 (United States); Xie, Jinqiao; Mita, Seiji [HexaTech, Inc., 991 Aviation Pkwy., Suite 800, Morrisville, North Carolina 27560 (United States)

    2015-04-06

    The internal quantum efficiency (IQE) of Al{sub 0.55}Ga{sub 0.45}N/AlN and Al{sub 0.55}Ga{sub 0.45}N/Al{sub 0.85}Ga{sub 0.15}N UVC MQW structures was analyzed. The use of bulk AlN substrates enabled us to undoubtedly distinguish the effect of growth conditions, such as V/III ratio, on the optical quality of AlGaN based MQWs from the influence of dislocations. At a high V/III ratio, a record high IQE of ∼80% at a carrier density of 10{sup 18 }cm{sup −3} was achieved at ∼258 nm. The high IQE was correlated with the decrease of the non-radiative coefficient A and a reduction of midgap defect luminescence, all suggesting that, in addition to dislocations, point defects are another major factor that strongly influences optical quality of AlGaN MQW structures.

  4. A quantum chemistry study on surface reactivity of pristine and carbon-substituted AlN nanotubes

    Science.gov (United States)

    Mahdaviani, Amir; Esrafili, Mehdi D.; Esrafili, Ali; Behzadi, Hadi

    2013-09-01

    A density functional theory investigation was performed to predict the surface reactivity of pristine and carbon-substituted (6,0) single-walled aluminum nitride nanotubes (AlNNTs). The properties determined include the electrostatic potentials VS(r) and average local ionization energies ĪS(r) on the surfaces of the investigated tubes. According to computed VS(r) results, the Al/N atoms in edge or cap regions show a different reactivity pattern than those at the middle portion of the tubes. Due to the carbon-substitution at the either Al or N sites of the tubes, the negative regions associated with nitrogen atoms are stronger than before. The prediction of surface reactivity and regioselectivity using average local ionization energies has been verified by atomic hydrogen chemisorption energies calculated for AlNNTs at the B3LYP/6-31 G* level. There is an acceptable correlation between the minima of ĪS(r) and the atomic hydrogen chemisorption energies, demonstrating that ĪS(r) provides an effective means for rapidly and economically assessing the relative reactivities of finite sized AlNNTs.

  5. Renal Pathology in a Nontraditional Aging Model: The Naked Mole-Rat (Heterocephalus glaber).

    Science.gov (United States)

    Delaney, M A; Kinsel, M J; Treuting, P M

    2016-03-01

    The naked mole-rat (NMR; Heterocephalus glaber) is growing in popularity as a model for aging research due to its extreme longevity (up to 30 years), highly adapted physiology, and resistance to cancer, particularly when compared with traditional aging models such as laboratory mice and rats. Despite the NMR's seemingly lengthy health span, several age-related lesions have been documented. During a 15-year retrospective evaluation of a zoo-housed population, histologic changes in the kidneys were reported in 127 of 138 (92%) adult NMRs. Of these, renal tubular mineralization was very common (115 of 127; 90.6%) and found in NMRs without concurrent renal lesions (36 of 127; 28.3%). Many of the other described lesions were considered progressive stages of a single process, generally referred to as chronic nephritis or nephropathy, and diagnosed in 73 of 127 (57.5%), while end-stage renal disease was reported in only 12 (9.4%) NMRs. Renal lesions of these NMRs were comparable to disease entities reported in laboratory rats and certain strains of inbred and noninbred mice. Although many lesions of NMR kidneys were similar to those found in aged laboratory rodents, some common urinary diseases were not represented in the examined colonies. The goal of this study was to describe renal lesions in NMRs from a zoologic setting to familiarize investigators and pathologists with an apparently common and presumably age-related disease in this nontraditional model. © The Author(s) 2015.

  6. Naked Mole Rat Induced Pluripotent Stem Cells and Their Contribution to Interspecific Chimera

    Directory of Open Access Journals (Sweden)

    Sang-Goo Lee

    2017-11-01

    Full Text Available Naked mole rats (NMRs are exceptionally long-lived, cancer-resistant rodents. Identifying the defining characteristics of these traits may shed light on aging and cancer mechanisms. Here, we report the generation of induced pluripotent stem cells (iPSCs from NMR fibroblasts and their contribution to mouse-NMR chimeric embryos. Efficient reprogramming could be observed under N2B27+2i conditions. The iPSCs displayed a characteristic morphology, expressed pluripotent markers, formed embryoid bodies, and showed typical differentiation patterns. Interestingly, NMR embryonic fibroblasts and the derived iPSCs had propensity for a tetraploid karyotype and were resistant to forming teratomas, but within mouse blastocysts they contributed to both interspecific placenta and fetus. Gene expression patterns of NMR iPSCs were more similar to those of human than mouse iPSCs. Overall, we uncovered unique features of NMR iPSCs and report a mouse-NMR chimeric model. The iPSCs and associated cell culture systems can be used for a variety of biological and biomedical applications.

  7. Functional characteristics of the naked mole rat μ-opioid receptor.

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    Melanie Busch-Dienstfertig

    Full Text Available While humans and most animals respond to µ-opioid receptor (MOR agonists with analgesia and decreased aggression, in the naked mole rat (NMR opioids induce hyperalgesia and severe aggression. Single nucleotide polymorphisms in the human mu-opioid receptor gene (OPRM1 can underlie altered behavioral responses to opioids. Therefore, we hypothesized that the primary structure of the NMR MOR may differ from other species. Sequencing of the NMR oprm1 revealed strong homology to other mammals, but exposed three unique amino acids that might affect receptor-ligand interactions. The NMR and rat oprm1 sequences were cloned into mammalian expression vectors and transfected into HEK293 cells. Radioligand binding and 3'-5'-cyclic adenosine monophosphate (cAMP enzyme immunoassays were used to compare opioid binding and opioid-mediated cAMP inhibition. At normalized opioid receptor protein levels we detected significantly lower [3H]DAMGO binding to NMR compared to rat MOR, but no significant difference in DAMGO-induced cAMP inhibition. Strong DAMGO-induced MOR internalization was detectable using radioligand binding and confocal imaging in HEK293 cells expressing rat or NMR receptor, while morphine showed weak or no effects. In summary, we found minor functional differences between rat and NMR MOR suggesting that other differences e.g. in anatomical distribution of MOR underlie the NMR's extreme reaction to opioids.

  8. Naked Mole Rat Cells Have a Stable Epigenome that Resists iPSC Reprogramming

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    Li Tan

    2017-11-01

    Full Text Available Naked mole rat (NMR is a valuable model for aging and cancer research due to its exceptional longevity and cancer resistance. We observed that the reprogramming efficiency of NMR fibroblasts in response to OSKM was drastically lower than that of mouse fibroblasts. Expression of SV40 LargeT antigen (LT dramatically improved reprogramming of NMR fibroblasts. Inactivation of Rb alone, but not p53, was sufficient to improve reprogramming efficiency, suggesting that NMR chromatin may be refractory to reprogramming. Analysis of the global histone landscape revealed that NMR had higher levels of repressive H3K27 methylation marks and lower levels of activating H3K27 acetylation marks than mouse. ATAC-seq revealed that in NMR, promoters of reprogramming genes were more closed than mouse promoters, while expression of LT led to massive opening of the NMR promoters. These results suggest that NMR displays a more stable epigenome that resists de-differentiation, contributing to the cancer resistance and longevity of this species.

  9. Individualistic approach to the management of complete hydatidiform mole with coexisting live fetus.

    Science.gov (United States)

    Rohilla, Minakshi; Singh, Purnima; Kaur, Jaswinder; Jain, Vanita; Gupta, Nalini; Prasad, G R V

    2015-08-01

    Complete hydatidiform mole with a coexisting live fetus (CHMCF) is a rare obstetric occurrence. So far, approximately 177 cases have been documented in the literature with consequent 66 live births. We report a review article along with two cases of CHMCF, one presenting as incomplete abortion and other continued as CHMCF but terminated because of antepartum hemorrhage. Both had histopathologically proven one normal and other complete molar placenta with coexisting normal fetus. No evidence of persistent trophoblastic disease was observed. The dilemma of continuation versus termination of pregnancy is being emphasized in the review of literature. Pregnancy complicated by CHMCF may result in a viable live born infant in approximately one third of the cases. A potentially viable fetus with CHMCF may result in normal live birth with antecedent high risk maternal complications. A decision of termination of pregnancy in all CHMCF will however nullify all the chances of a live birth. An individualistic approach and an informed doctor patient consensus may improve the likely outcome. Appropriate counseling of the mother regarding high incidence of antenatal complications plays an integral part of decision of continuation of such pregnancies. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.

  10. Antagonistic Coevolution Drives Whack-a-Mole Sensitivity in Gene Regulatory Networks.

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    Jeewoen Shin

    2015-10-01

    Full Text Available Robustness, defined as tolerance to perturbations such as mutations and environmental fluctuations, is pervasive in biological systems. However, robustness often coexists with its counterpart, evolvability--the ability of perturbations to generate new phenotypes. Previous models of gene regulatory network evolution have shown that robustness evolves under stabilizing selection, but it is unclear how robustness and evolvability will emerge in common coevolutionary scenarios. We consider a two-species model of coevolution involving one host and one parasite population. By using two interacting species, key model parameters that determine the fitness landscapes become emergent properties of the model, avoiding the need to impose these parameters externally. In our study, parasites are modeled on species such as cuckoos where mimicry of the host phenotype confers high fitness to the parasite but lower fitness to the host. Here, frequent phenotype changes are favored as each population continually adapts to the other population. Sensitivity evolves at the network level such that point mutations can induce large phenotype changes. Crucially, the sensitive points of the network are broadly distributed throughout the network and continually relocate. Each time sensitive points in the network are mutated, new ones appear to take their place. We have therefore named this phenomenon "whack-a-mole" sensitivity, after a popular fun park game. We predict that this type of sensitivity will evolve under conditions of strong directional selection, an observation that helps interpret existing experimental evidence, for example, during the emergence of bacterial antibiotic resistance.

  11. The influence of field margins on the presence and spatial distribution of the European mole Talpa europaea L. within the agricultural landscape of northern Poland

    Directory of Open Access Journals (Sweden)

    Zurawska-Seta Ewa

    2012-01-01

    Full Text Available European moles are widespread in both cultivated and uncultivated areas in Poland. Their occurrence and distribution in relation to the physical and chemical characteristics of soil has been already studied in previous research. However, there is still an open question about the impact of the structure of anthropogenic habitats produced by agriculture on moles. The main aim of this study is to assess the influence of different kinds of field margins on the presence and spatial distribution of the European mole Talpa europaea L. in farmlands. Methods included the monitoring of six investigative sites in northern Poland. Observations were made during three six-month periods in 2005-2008 of the presence or absence of moles as recognized by recent molehills and surface tunnels. There was a very clear tendency by moles to occupy areas within arable fields close to field boundaries with wide verges containing ruderal and woodland communities with a spacious zone of ecotones. Narrow boundary strips were avoided by moles. In conclusion, the conducted research confirms that field margins have an impact on the presence and spatial distribution of moles within ploughed lands. Our results may be helpful in improving the relation between agricultural development and biodiversity conservation, and the rational use of nature by humankind.

  12. RNA sequencing reveals differential expression of mitochondrial and oxidation reduction genes in the long-lived naked mole-rat when compared to mice.

    Science.gov (United States)

    Yu, Chuanfei; Li, Yang; Holmes, Andrew; Szafranski, Karol; Faulkes, Chris G; Coen, Clive W; Buffenstein, Rochelle; Platzer, Matthias; de Magalhães, João Pedro; Church, George M

    2011-01-01

    The naked mole-rat (Heterocephalus glaber) is a long-lived, cancer resistant rodent and there is a great interest in identifying the adaptations responsible for these and other of its unique traits. We employed RNA sequencing to compare liver gene expression profiles between naked mole-rats and wild-derived mice. Our results indicate that genes associated with oxidoreduction and mitochondria were expressed at higher relative levels in naked mole-rats. The largest effect is nearly 300-fold higher expression of epithelial cell adhesion molecule (Epcam), a tumour-associated protein. Also of interest are the protease inhibitor, alpha2-macroglobulin (A2m), and the mitochondrial complex II subunit Sdhc, both ageing-related genes found strongly over-expressed in the naked mole-rat. These results hint at possible candidates for specifying species differences in ageing and cancer, and in particular suggest complex alterations in mitochondrial and oxidation reduction pathways in the naked mole-rat. Our differential gene expression analysis obviated the need for a reference naked mole-rat genome by employing a combination of Illumina/Solexa and 454 platforms for transcriptome sequencing and assembling transcriptome contigs of the non-sequenced species. Overall, our work provides new research foci and methods for studying the naked mole-rat's fascinating characteristics.

  13. Adult naked mole-rat brain retains the NMDA receptor subunit GluN2D associated with hypoxia tolerance in neonatal mammals.

    Science.gov (United States)

    Peterson, Bethany L; Park, Thomas J; Larson, John

    2012-01-11

    Adult naked mole-rats show a number of systemic adaptations to a crowded underground habitat that is low in oxygen and high in carbon dioxide. Remarkably, brain slice tissue from adult naked mole-rats also is extremely tolerant to oxygen deprivation as indicated by maintenance of synaptic transmission under hypoxic conditions as well as by a delayed neuronal depolarization during anoxia. These characteristics resemble hypoxia tolerance in brain slices from neonates in a variety of mammal species. An important component of neonatal tolerance to hypoxia involves the subunit composition of NMDA receptors. Neonates have a high proportion of NMDA receptors with GluN2D subunits which are protective because they retard calcium entry into neurons during hypoxic episodes. Therefore, we hypothesized that adult naked mole-rats retain a protective, neonatal-like, NMDA receptor subunit profile. We used immunoblotting to assess age-related changes in NMDA receptor subunits in naked mole-rats and mice. The results show that adult naked mole-rat brain retains a much greater proportion of the hypoxia-protective GluN2D subunit compared to adult mice. However, age-related changes in other subunits (GluN2A and GluN2B) from the neonatal period to adulthood were comparable in mice and naked mole-rats. Hence, adult naked mole-rat brain only retains the neonatal NMDA receptor subunit that is associated with hypoxia tolerance. Copyright © 2011 Elsevier Ireland Ltd. All rights reserved.

  14. RNA sequencing reveals differential expression of mitochondrial and oxidation reduction genes in the long-lived naked mole-rat when compared to mice.

    Directory of Open Access Journals (Sweden)

    Chuanfei Yu

    Full Text Available The naked mole-rat (Heterocephalus glaber is a long-lived, cancer resistant rodent and there is a great interest in identifying the adaptations responsible for these and other of its unique traits. We employed RNA sequencing to compare liver gene expression profiles between naked mole-rats and wild-derived mice. Our results indicate that genes associated with oxidoreduction and mitochondria were expressed at higher relative levels in naked mole-rats. The largest effect is nearly 300-fold higher expression of epithelial cell adhesion molecule (Epcam, a tumour-associated protein. Also of interest are the protease inhibitor, alpha2-macroglobulin (A2m, and the mitochondrial complex II subunit Sdhc, both ageing-related genes found strongly over-expressed in the naked mole-rat. These results hint at possible candidates for specifying species differences in ageing and cancer, and in particular suggest complex alterations in mitochondrial and oxidation reduction pathways in the naked mole-rat. Our differential gene expression analysis obviated the need for a reference naked mole-rat genome by employing a combination of Illumina/Solexa and 454 platforms for transcriptome sequencing and assembling transcriptome contigs of the non-sequenced species. Overall, our work provides new research foci and methods for studying the naked mole-rat's fascinating characteristics.

  15. Interface/border trap characterization of Al{sub 2}O{sub 3}/AlN/GaN metal-oxide-semiconductor structures with an AlN interfacial layer

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Shenghou; Yang, Shu; Tang, Zhikai; Jiang, Qimeng; Liu, Cheng; Chen, Kevin J., E-mail: eekjchen@ust.hk [Department of Electronic and Computer Engineering, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon (Hong Kong); Wang, Maojun [Institute of Microelectronics, Peking University, Beijing 100871 (China); Shen, Bo [School of Physics, Peking University, Beijing 100871 (China)

    2015-02-02

    We report the interface characterization of Al{sub 2}O{sub 3}/AlN/GaN MOS (metal-oxide-semiconductor) structures with an AlN interfacial layer. A thin monocrystal-like interfacial layer (AlN) is formed at the Al{sub 2}O{sub 3}/GaN to effectively block oxygen from the GaN surface and prevent the formation of detrimental Ga-O bonds. The suppression of Ga-O bonds is validated by X-ray photoelectron spectroscopy of the critical interface. Frequency-dispersion in C-V characteristics has been significantly reduced, owing to improved interface quality. Furthermore, using the conventional conductance method suitable for extracting the interface trap density D{sub it} in MOS structures, D{sub it} in the device with AlN was determined to be in the range of 10{sup 11}–10{sup 12 }eV{sup −1 }cm{sup −2}, showing one order of magnitude lower than that without AlN. Border traps near the gate-dielectric/GaN interface were identified and shown to be suppressed by the AlN interfacial layer as well.

  16. Fractional and noncommutative spacetimes

    NARCIS (Netherlands)

    Arzano, M.|info:eu-repo/dai/nl/32616443X; Calcagni, M.; Oriti, D.; Scalisi, M.

    2011-01-01

    We establish a mapping between fractional and noncommutative spacetimes in configuration space. Depending on the scale at which the relation is considered, there arise two possibilities. For a fractional spacetime with log-oscillatory measure, the effective measure near the fundamental scale

  17. Fractional location problems

    NARCIS (Netherlands)

    A.I. Barros (Ana); J.B.G. Frenk (Hans); J.A.S. Gromicho (Joaquim)

    1997-01-01

    textabstractIn this paper we analyze some variants of the classical uncapacitated facility location problem with a ratio as an objective function. Using basic concepts and results of fractional programming, we identify a class of one-level fractional location problems which can be solved in

  18. An Appetite for Fractions

    Science.gov (United States)

    Wilkerson, Trena L.; Bryan, Tommy; Curry, Jane

    2012-01-01

    This article describes how using candy bars as models gives sixth-grade students a taste for learning to represent fractions whose denominators are factors of twelve. Using paper models of the candy bars, students explored and compared fractions. They noticed fewer different representations for one-third than for one-half. The authors conclude…

  19. Fractional bosonic strings

    Science.gov (United States)

    Diaz, Victor Alfonzo; Giusti, Andrea

    2018-03-01

    The aim of this paper is to present a simple generalization of bosonic string theory in the framework of the theory of fractional variational problems. Specifically, we present a fractional extension of the Polyakov action, for which we compute the general form of the equations of motion and discuss the connection between the new fractional action and a generalization the Nambu-Goto action. Consequently, we analyze the symmetries of the modified Polyakov action and try to fix the gauge, following the classical procedures. Then we solve the equations of motion in a simplified setting. Finally, we present a Hamiltonian description of the classical fractional bosonic string and introduce the fractional light-cone gauge. It is important to remark that, throughout the whole paper, we thoroughly discuss how to recover the known results as an "integer" limit of the presented model.

  20. Complete Hydatidiform Mole Presenting as a Placenta Accreta in a Twin Pregnancy with a Coexisting Normal Fetus: Case Report

    Directory of Open Access Journals (Sweden)

    Marijo Aguilera

    2012-01-01

    Full Text Available A twin pregnancy with a complete hydatidiform mole and a coexisting normal fetus (CHMF is a rare clinical scenario, and it carries many associated pregnancy and postnatal risks. Limited numbers of case studies exist reporting an outcome of live birth, and only three prior cases report the presentation of a hydatidiform mole as a placenta previa. We report a case of CHMF with the molar component presenting antenatally as a placenta previa, which ultimately resulted in placenta accreta at the time of delivery. A live male infant was delivered at 34 weeks’ gestation via planned cesarean section, and a hysterectomy was performed following unsuccessful removal of the molar component. We additionally utilized previously described methods of placing internal iliac balloons and ureteral stents prior to delivery. In such a high-risk pregnancy with a known molar previa component, these surgical preparation measures may be of benefit.

  1. The effects of oxotremorine, epibatidine, atropine, mecamylamine and naloxone in the tail-flick, hot-plate, and formalin tests in the naked mole-rat (Heterocephalus glaber)

    DEFF Research Database (Denmark)

    Dulu, Thomas D; Kanui, Titus I; Towett, Philemon K

    2014-01-01

    The naked mole-rat (Heterocephalus glaber) is a promising animal model for the study of pain mechanisms, therefore a thorough characterization of this species is essential. The aim of the present study was to establish the naked mole-rat as a model for studying the cholinergic receptor system....... The present study demonstrated that stimulation of muscarinic and nicotinic receptors produces antinociceptive effects in the naked-mole rat. The reversal effect of atropine and mecamylamine suggests that this effect is mediated by cholinergic receptors. As naloxone increases the antinociceptive effects...

  2. Multiple primary cutaneous melanomas in patients with FAMMM syndrome and sporadic atypical mole syndrome (AMS): what's worse?

    Science.gov (United States)

    Tchernev, Georgi; Ananiev, Julian; Cardoso, José-Carlos; Chokoeva, Anastasiya Atanasova; Philipov, Stanislav; Penev, Plamen Kolev; Lotti, Torello; Wollina, Uwe

    2014-08-01

    Atypical Mole Syndrome is the most important phenotypic risk factor for cutaneous melanoma, a malignancy that accounts for about 80% of deaths from skin cancer. Since early diagnosis of melanoma is of great prognostic relevance, the identification of Atypical Mole Syndrome carriers (sporadic and familial) is essential, as well as the recommendation of preventative measures that must be undertaken by these patients.We report two rare cases concerning patients with multiple primary skin melanomas in the setting of a familial and a sporadic syndrome of dysplastic nevi: the first patient is a 67-year-old patient with a history of multiple superficial spreading melanomas localized on his back. The second patient presented with multiple primary melanomas in advanced stage in the context of the so-called sporadic form of the syndrome of dysplastic nevi-AMS (atypical mole syndrome). In the first case, excision of the melanomas was carried out with an uneventful post-operative period. In the second case, disseminated metastases were detected, involving the right fibula, the abdominal cavity as well as multiple lesions in the brain. The patient declined BRAF mutation tests as well as chemotherapy or targeted therapies, and suffered a rapid deterioration in his general condition leading to death. We classified the second case as a sporadic form of the atypical mole syndrome, associated with one nodular and two superficial spreading melanomas.There are no data in the literature to allow us to understand if, in patients with multiple primary melanomas, there is any difference in terms of prognosis between those with and without a family history of a similar phenotype. To answer this and other questions related to these rare cases, further studies with a significant number of patients should be carried out.

  3. High specific activity N-Acetyl-3H-α-Aspartyl- L-Glutamic at micro mole scale

    International Nuclear Information System (INIS)

    Suarez, C.

    1984-01-01

    High specific activity N-Acetyl-3 H - α -Aspartyl-I-Glutamic acid at micro mole scale in prepared acetylating L- α -Aspartyl-L-glutamic with 3 H -acetic anhydride in re distilled toluene. The product le purified through cationic and anionic columns. The radiochemical purity as determined by thin-layer chromatography is greater then 99% at the time preparation. (Author) 5 refs

  4. Challenging the inbreeding hypothesis in a eusocial mammal: population genetics of the naked mole-rat, Heterocephalus glaber.

    Science.gov (United States)

    Ingram, Colleen M; Troendle, Nicholas J; Gill, Clare A; Braude, Stanton; Honeycutt, Rodney L

    2015-10-01

    The role of genetic relatedness in the evolution of eusociality has been the topic of much debate, especially when contrasting eusocial insects with vertebrates displaying reproductive altruism. The naked mole-rat, Heterocephalus glaber, was the first described eusocial mammal. Although this discovery was based on an ecological constraints model of eusocial evolution, early genetic studies reported high levels of relatedness in naked mole-rats, providing a compelling argument that low dispersal rates and consanguineous mating (inbreeding as a mating system) are the driving forces for the evolution of this eusocial species. One caveat to accepting this long-held view is that the original genetic studies were based on limited sampling from the species' geographic distribution. A growing body of evidence supports a contrary view, with the original samples not representative of the species-rather reflecting a single founder event, establishing a small population south of the Athi River. Our study is the first to address these competing hypotheses by examining patterns of molecular variation in colonies sampled from north and south of the Athi and Tana rivers, which based on our results, serve to isolate genetically distinct populations of naked mole-rats. Although colonies south of the Athi River share a single mtDNA haplotype and are fixed at most microsatellite loci, populations north of the Athi River are considerably more variable. Our findings support the position that the low variation observed in naked mole-rat populations south of the Athi River reflects a founder event, rather than a consequence of this species' unusual mating system. © 2015 John Wiley & Sons Ltd.

  5. Naked mole-rats maintain healthy skeletal muscle and Complex IV mitochondrial enzyme function into old age.

    Science.gov (United States)

    Stoll, Elizabeth A; Karapavlovic, Nevena; Rosa, Hannah; Woodmass, Michael; Rygiel, Karolina; White, Kathryn; Turnbull, Douglass M; Faulkes, Chris G

    2016-12-19

    The naked mole-rat (NMR) Heterocephalus glaber is an exceptionally long-lived rodent, living up to 32 years in captivity. This extended lifespan is accompanied by a phenotype of negligible senescence, a phenomenon of very slow changes in the expected physiological characteristics with age. One of the many consequences of normal aging in mammals is the devastating and progressive loss of skeletal muscle, termed sarcopenia, caused in part by respiratory enzyme dysfunction within the mitochondria of skeletal muscle fibers. Here we report that NMRs avoid sarcopenia for decades. Muscle fiber integrity and mitochondrial ultrastructure are largely maintained in aged animals. While mitochondrial Complex IV expression and activity remains stable, Complex I expression is significantly decreased. We show that aged naked mole-rat skeletal muscle tissue contains some mitochondrial DNA rearrangements, although the common mitochondrial DNA deletions associated with aging in human and other rodent skeletal muscles are not present. Interestingly, NMR skeletal muscle fibers demonstrate a significant increase in mitochondrial DNA copy number. These results have intriguing implications for the role of mitochondria in aging, suggesting Complex IV, but not Complex I, function is maintained in the long-lived naked mole rat, where sarcopenia is avoided and healthy muscle function is maintained for decades.

  6. Cessation of reproduction-related spine elongation after multiple breeding cycles in female naked mole-rats.

    Science.gov (United States)

    Dengler-Crish, Christine M; Catania, Kenneth C

    2009-01-01

    The breeding female or "queen" naked mole-rat has a uniquely elongated body morphology attributed to the lengthening of the lumbar vertebral column that occurs during pregnancy. It is unknown whether this vertebral growth is a continuous process, or associated only with early reproductive experience. We compared pregnancy-related bone elongation in nascent primiparous queens and established queens to determine if this vertebral expansion was a lifelong process in these females. We also investigated the impact of lactation on vertebral elongation in these mole-rats because it is known to be a time of significant bone loss in other mammals. Our data show that after eight or more pregnancies, established queens no longer experienced a net gain in lumbar spine length over the reproductive cycle, whereas the nascent breeders demonstrated significant spine lengthening over this time. Despite the lack of net spine lengthening in established breeders, our results indicated that these queens still experienced some pregnancy-specific vertebral elongation. In naked mole-rats, pregnancy-induced bone elongation may serve the dual purposes of first lengthening the spine, and then once optimal spine size is achieved, serving as a homeostatic mechanism that prepares the spine for the mineral demands of lactation. Anat Rec, 2009. (c) 2008 Wiley-Liss, Inc.

  7. Initial Case Reports of Cancer in Naked Mole-rats (Heterocephalus glaber).

    Science.gov (United States)

    Delaney, M A; Ward, J M; Walsh, T F; Chinnadurai, S K; Kerns, K; Kinsel, M J; Treuting, P M

    2016-05-01

    Naked mole-rats (NMRs;Heterocephalus glaber) are highly adapted, eusocial rodents renowned for their extreme longevity and resistance to cancer. Because cancer has not been formally described in this species, NMRs have been increasingly utilized as an animal model in aging and cancer research. We previously reported the occurrence of several age-related diseases, including putative pre-neoplastic lesions, in zoo-housed NMR colonies. Here, we report for the first time 2 cases of cancer in zoo-housed NMRs. In Case No. 1, we observed a subcutaneous mass in the axillary region of a 22-year-old male NMR, with histologic, immunohistochemical (pancytokeratin positive, rare p63 immunolabeling, and smooth muscle actin negative), and ultrastructural characteristics of an adenocarcinoma possibly of mammary or salivary origin. In Case No. 2, we observed a densely cellular, poorly demarcated gastric mass of polygonal cells arranged in nests with positive immunolabeling for synaptophysin and chromogranin indicative of a neuroendocrine carcinoma in an approximately 20-year-old male NMR. We also include a brief discussion of other proliferative growths and pre-cancerous lesions diagnosed in 1 zoo colony. Although these case reports do not alter the longstanding observation of cancer resistance, they do raise questions about the scope of cancer resistance and the interpretation of biomedical studies in this model. These reports also highlight the benefit of long-term disease investigations in zoo-housed populations to better understand naturally occurring disease processes in species used as models in biomedical research. © The Author(s) 2016.

  8. The Insulin-Like Growth Factor System in the Long-Lived Naked Mole-Rat.

    Science.gov (United States)

    Brohus, Malene; Gorbunova, Vera; Faulkes, Chris G; Overgaard, Michael T; Conover, Cheryl A

    2015-01-01

    Naked mole-rats (Heterocephalus glaber) (NMRs) are the longest living rodents known. They show negligible senescence, and are resistant to cancers and certain damaging effects associated with aging. The insulin-like growth factors (IGFs) have pluripotent actions, influencing growth processes in virtually every system of the body. They are established contributors to the aging process, confirmed by the demonstration that decreased IGF signaling results in life-extending effects in a variety of species. The IGFs are likewise involved in progression of cancers by mediating survival signals in malignant cells. This report presents a full characterization of the IGF system in the NMR: ligands, receptors, IGF binding proteins (IGFBPs), and IGFBP proteases. A particular emphasis was placed on the IGFBP protease, pregnancy-associated plasma protein-A (PAPP-A), shown to be an important lifespan modulator in mice. Comparisons of IGF-related genes in the NMR with human and murine sequences indicated no major differences in essential parts of the IGF system, including PAPP-A. The protease was shown to possess an intact active site despite the report of a contradictory genome sequence. Furthermore, PAPP-A was expressed and translated in NMRs cells and retained IGF-dependent proteolytic activity towards IGFBP-4 and IGF-independent activity towards IGFBP-5. However, experimental data suggest differential regulatory mechanisms for PAPP-A expression in NMRs than those described in humans and mice. This overall description of the IGF system in the NMR represents an initial step towards elucidating the complex molecular mechanisms underlying longevity, and how these animals have evolved to ensure a delayed and healthy aging process.

  9. Transcriptome sequencing of the naked mole rat (Heterocephalus glaber and identification of hypoxia tolerance genes

    Directory of Open Access Journals (Sweden)

    Bang Xiao

    2017-12-01

    Full Text Available The naked mole rat (NMR; Heterocephalus glaber is a small rodent species found in regions of Kenya, Ethiopia and Somalia. It has a high tolerance for hypoxia and is thus considered one of the most important natural models for studying hypoxia tolerance mechanisms. The various mechanisms underlying the NMR's hypoxia tolerance are beginning to be understood at different levels of organization, and next-generation sequencing methods promise to expand this understanding to the level of gene expression. In this study, we examined the sequence and transcript abundance data of the muscle transcriptome of NMRs exposed to hypoxia using the Illumina HiSeq 2500 system to clarify the possible genomic adaptive responses to the hypoxic underground surroundings. The RNA-seq raw FastQ data were mapped against the NMR genome. We identified 2337 differentially expressed genes (DEGs by comparison of the hypoxic and control groups. Functional annotation of the DEGs by gene ontology (GO analysis revealed enrichment of hypoxia stress-related GO categories, including ‘biological regulation’, ‘cellular process’, ‘ion transport’ and ‘cell-cell signaling’. Enrichment of DEGs in signaling pathways was analyzed against the Kyoto Encyclopedia of Genes and Genomes (KEGG database to identify possible interactions between DEGs. The results revealed significant enrichment of DEGs in focal adhesion, the mitogen-activated protein kinase (MAPK signaling pathway and the glycine, serine and threonine metabolism pathway. Furthermore, inhibition of DEGs (STMN1, MAPK8IP1 and MAPK10 expression induced apoptosis and arrested cell growth in NMR fibroblasts following hypoxia. Thus, this global transcriptome analysis of NMRs can provide an important genetic resource for the study of hypoxia tolerance in mammals. Furthermore, the identified DEGs may provide important molecular targets for biomedical research into therapeutic strategies for stroke and cardiovascular diseases.

  10. The Insulin-Like Growth Factor System in the Long-Lived Naked Mole-Rat.

    Directory of Open Access Journals (Sweden)

    Malene Brohus

    Full Text Available Naked mole-rats (Heterocephalus glaber (NMRs are the longest living rodents known. They show negligible senescence, and are resistant to cancers and certain damaging effects associated with aging. The insulin-like growth factors (IGFs have pluripotent actions, influencing growth processes in virtually every system of the body. They are established contributors to the aging process, confirmed by the demonstration that decreased IGF signaling results in life-extending effects in a variety of species. The IGFs are likewise involved in progression of cancers by mediating survival signals in malignant cells. This report presents a full characterization of the IGF system in the NMR: ligands, receptors, IGF binding proteins (IGFBPs, and IGFBP proteases. A particular emphasis was placed on the IGFBP protease, pregnancy-associated plasma protein-A (PAPP-A, shown to be an important lifespan modulator in mice. Comparisons of IGF-related genes in the NMR with human and murine sequences indicated no major differences in essential parts of the IGF system, including PAPP-A. The protease was shown to possess an intact active site despite the report of a contradictory genome sequence. Furthermore, PAPP-A was expressed and translated in NMRs cells and retained IGF-dependent proteolytic activity towards IGFBP-4 and IGF-independent activity towards IGFBP-5. However, experimental data suggest differential regulatory mechanisms for PAPP-A expression in NMRs than those described in humans and mice. This overall description of the IGF system in the NMR represents an initial step towards elucidating the complex molecular mechanisms underlying longevity, and how these animals have evolved to ensure a delayed and healthy aging process.

  11. Effects of total-body digital photography on cancer worry in patients with atypical mole syndrome.

    Science.gov (United States)

    Moye, Molly S; King, Sallyann M C; Rice, Zakiya P; DeLong, Laura K; Seidler, Anne M; Veledar, Emir; Curiel-Lewandrowski, Clara; Chen, Suephy C

    2015-02-01

    Cancer worry about developing melanoma in at-risk patients may affect one's quality of life and adherence to screening. Little is known about melanoma-related worry in patients with atypical mole syndrome (AMS). To quantify levels and elucidate predictors of worry related to developing melanoma in patients with AMS and to determine whether total-body digital photography (TBDP) in pigmented lesion clinics (PLCs) reduces worry. In this pretest-posttest study, patients with AMS from PLCs at 2 academic medical centers were recruited from June 1, 2005, through October 31, 2008, to answer questions about cancer worry before and after undergoing TBDP. Questionnaires used included the new melanoma and recurrent melanoma Revised Impact of Event Scale (RIES), the Melanoma Worry Scale (MWS), the Hospital Anxiety and Depression Scale, and the Life Orientation Test. All patients underwent TBDP. Changes in the MWS and new melanoma RIES scores. A total of 138 patients completed baseline questionnaires; 108 patients (78.3%) completed questionnaires after TBDP. Baseline levels of worry were low and reduced further after TBDP. In patients with a personal history of melanoma, worry was reduced on all scales. In patients without a personal history of melanoma, only the new melanoma RIES score was significantly decreased. Predictors of baseline MWS scores include female sex, personal history of melanoma, and higher Hospital Anxiety and Depression Scale scores, adjusted for demographics, family history of melanoma, and Life Orientation Test scores. Adjusted predictors of the baseline new melanoma RIES score were similar but also included lower educational level and did not include sex. Patients with AMS have low levels of melanoma-related worry, which is similar to data from other populations at high risk of cancers. We found that TBDP is a clinically useful tool that can be used in PLCs to help decrease worry about developing melanoma in at-risk patients.

  12. Fractional Order Generalized Information

    Directory of Open Access Journals (Sweden)

    José Tenreiro Machado

    2014-04-01

    Full Text Available This paper formulates a novel expression for entropy inspired in the properties of Fractional Calculus. The characteristics of the generalized fractional entropy are tested both in standard probability distributions and real world data series. The results reveal that tuning the fractional order allow an high sensitivity to the signal evolution, which is useful in describing the dynamics of complex systems. The concepts are also extended to relative distances and tested with several sets of data, confirming the goodness of the generalization.

  13. FRACTIONS: CONCEPTUAL AND DIDACTIC ASPECTS

    Directory of Open Access Journals (Sweden)

    Sead Rešić

    2016-09-01

    Full Text Available Fractions represent the manner of writing parts of whole numbers (integers. Rules for operations with fractions differ from rules for operations with integers. Students face difficulties in understanding fractions, especially operations with fractions. These difficulties are well known in didactics of Mathematics throughout the world and there is a lot of research regarding problems in learning about fractions. Methods for facilitating understanding fractions have been discovered, which are essentially related to visualizing operations with fractions.

  14. Fractional Stochastic Field Theory

    Science.gov (United States)

    Honkonen, Juha

    2018-02-01

    Models describing evolution of physical, chemical, biological, social and financial processes are often formulated as differential equations with the understanding that they are large-scale equations for averages of quantities describing intrinsically random processes. Explicit account of randomness may lead to significant changes in the asymptotic behaviour (anomalous scaling) in such models especially in low spatial dimensions, which in many cases may be captured with the use of the renormalization group. Anomalous scaling and memory effects may also be introduced with the use of fractional derivatives and fractional noise. Construction of renormalized stochastic field theory with fractional derivatives and fractional noise in the underlying stochastic differential equations and master equations and the interplay between fluctuation-induced and built-in anomalous scaling behaviour is reviewed and discussed.

  15. Social Trust and Fractionalization:

    DEFF Research Database (Denmark)

    Bjørnskov, Christian

    2008-01-01

    a much larger country sample than in previous literature confirms that fractionalization in the form of income inequality and political diversity adversely affects social trust while ethnic diversity does not. However, these effects differ systematically across countries, questioning standard...

  16. Fractional excretion of sodium

    Science.gov (United States)

    FE sodium; FENa ... a lab. There, they are examined for salt (sodium) and creatinine levels. Creatinine is a chemical waste ... Chernecky CC, Berger BJ. Excretion fraction of filtered sodium-blood and urine. In: Chernecky CC, Berger BJ, ...

  17. Discrete fractional calculus

    CERN Document Server

    Goodrich, Christopher

    2015-01-01

    This text provides the first comprehensive treatment of the discrete fractional calculus. Experienced researchers will find the text useful as a reference for discrete fractional calculus and topics of current interest. Students who are interested in learning about discrete fractional calculus will find this text to provide a useful starting point. Several exercises are offered at the end of each chapter and select answers have been provided at the end of the book. The presentation of the content is designed to give ample flexibility for potential use in a myriad of courses and for independent study. The novel approach taken by the authors includes a simultaneous treatment of the fractional- and integer-order difference calculus (on a variety of time scales, including both the usual forward and backwards difference operators). The reader will acquire a solid foundation in the classical topics of the discrete calculus while being introduced to exciting recent developments, bringing them to the frontiers of the...

  18. The Local Fractional Bootstrap

    DEFF Research Database (Denmark)

    Bennedsen, Mikkel; Hounyo, Ulrich; Lunde, Asger

    new resampling method, the local fractional bootstrap, relies on simulating an auxiliary fractional Brownian motion that mimics the fine properties of high frequency differences of the Brownian semistationary process under the null hypothesis. We prove the first order validity of the bootstrap method...... to two empirical data sets: we assess the roughness of a time series of high-frequency asset prices and we test the validity of Kolmogorov's scaling law in atmospheric turbulence data....

  19. Intracellular Cadmium Isotope Fractionation

    Science.gov (United States)

    Horner, T. J.; Lee, R. B.; Henderson, G. M.; Rickaby, R. E.

    2011-12-01

    Recent stable isotope studies into the biological utilization of transition metals (e.g. Cu, Fe, Zn, Cd) suggest several stepwise cellular processes can fractionate isotopes in both culture and nature. However, the determination of fractionation factors is often unsatisfactory, as significant variability can exist - even between different organisms with the same cellular functions. Thus, it has not been possible to adequately understand the source and mechanisms of metal isotopic fractionation. In order to address this problem, we investigated the biological fractionation of Cd isotopes within genetically-modified bacteria (E. coli). There is currently only one known biological use or requirement of Cd, a Cd/Zn carbonic anhydrase (CdCA, from the marine diatom T. weissfloggii), which we introduce into the E. coli genome. We have also developed a cleaning procedure that allows for the treating of bacteria so as to study the isotopic composition of different cellular components. We find that whole cells always exhibit a preference for uptake of the lighter isotopes of Cd. Notably, whole cells appear to have a similar Cd isotopic composition regardless of the expression of CdCA within the E. coli. However, isotopic fractionation can occur within the genetically modified E. coli during Cd use, such that Cd bound in CdCA can display a distinct isotopic composition compared to the cell as a whole. Thus, the externally observed fractionation is independent of the internal uses of Cd, with the largest Cd isotope fractionation occurring during cross-membrane transport. A general implication of these experiments is that trace metal isotopic fractionation most likely reflects metal transport into biological cells (either actively or passively), rather than relating to expression of specific physiological function and genetic expression of different metalloenzymes.

  20. Membrane phospholipid composition may contribute to exceptional longevity of the naked mole-rat (Heterocephalus glaber): a comparative study using shotgun lipidomics.

    Science.gov (United States)

    Mitchell, Todd W; Buffenstein, Rochelle; Hulbert, A J

    2007-11-01

    Phospholipids containing highly polyunsaturated fatty acids are particularly prone to peroxidation and membrane composition may therefore influence longevity. Phospholipid molecules, in particular those containing docosahexaenoic acid (DHA), from the skeletal muscle, heart, liver and liver mitochondria were identified and quantified using mass-spectrometry shotgun lipidomics in two similar-sized rodents that show an approximately 9-fold difference in maximum lifespan. The naked mole rat is the longest-living rodent known with a maximum lifespan of >28 years. Total phospholipid distribution is similar in tissues of both species; DHA is only found in phosphatidylcholines (PC), phosphatidylethanolamines (PE) and phosphatidylserines (PS), and DHA is relatively more concentrated in PE than PC. Naked mole-rats have fewer molecular species of both PC and PE than do mice. DHA-containing phospholipids represent 27-57% of all phospholipids in mice but only 2-6% in naked mole-rats. Furthermore, while mice have small amounts of di-polyunsaturated PC and PE, these are lacking in naked mole-rats. Vinyl ether-linked phospholipids (plasmalogens) are higher in naked mole-rat tissues than in mice. The lower level of DHA-containing phospholipids suggests a lower susceptibility to peroxidative damage in membranes of naked mole-rats compared to mice. Whereas the high level of plasmalogens might enhance membrane antioxidant protection in naked mole-rats compared to mice. Both characteristics possibly contribute to the exceptional longevity of naked mole-rats and may indicate a special role for peroxisomes in this extended longevity.

  1. High-resolution X-ray photoemission spectroscopy study of AlN nano-columns grown by nitridation of Al nano-squares on Si(111) substrates with ammonia

    International Nuclear Information System (INIS)

    Qi, B.; Agnarsson, B.; Goethelid, M.; Olafsson, S.; Gislason, H.P.

    2010-01-01

    The growth of AlN nano-columns by ammonium nitridation of Al nano-squares embedded in SiO 2 on Si(111) substrates was studied by high-resolution X-ray photoemission spectroscopy from a synchrotron radiation source and scanning electron microscopy (SEM). Selective nitridation of the Al nano-squares on the SiO 2 mask was obtained in the temperature window of 600 o C-700 o C. The well-shaped AlN nano-column arrays with diameters confined by the lateral size of the Al nano-squares (∼ 100 nm) were observed in SEM.

  2. Technical Note: Latitude-time variations of atmospheric column-average dry air mole fractions of CO2, CH4 and N2O

    Directory of Open Access Journals (Sweden)

    M. Rettinger

    2012-08-01

    Full Text Available We present a comparison of an atmospheric general circulation model (AGCM-based chemistry-transport model (ACTM simulation with total column measurements of CO2, CH4 and N2O from the Total Carbon Column Observing Network (TCCON. The model is able to capture observed trends, seasonal cycles and inter hemispheric gradients at most sampled locations for all three species. The model-observation agreements are best for CO2, because the simulation uses fossil fuel inventories and an inverse model estimate of non-fossil fuel fluxes. The ACTM captures much of the observed seasonal variability in CO2 and N2O total columns (~81 % variance, R>0.9 between ACTM and TCCON for 19 out of 22 cases. These results suggest that the transport processes in troposphere and stratosphere are well represented in ACTM. Thus the poor correlation between simulated and observed CH4 total columns, particularly at tropical and extra-tropical sites, have been attributed to the uncertainties in surface emissions and loss by hydroxyl radicals. While the upward-looking total column measurements of CO2 contains surface flux signals at various spatial and temporal scales, the N2O measurements are strongly affected by the concentration variations in the upper troposphere and stratosphere.

  3. Equation of state modeling of the phase equilibria of asymmetric CO2+n-alkane binary systems using mixing rules cubic with respect to mole fraction

    DEFF Research Database (Denmark)

    Cismondi, Martin; Mollerup, Jørgen M.; Zabaloy, Marcelo S.

    2010-01-01

    Both the equation of state (EOS) and the quadratic mixing rules proposed by van der Waals towards the end of the XIX century were enormous contributions to the understanding and modeling of fluids phase behavior. They set the basis for a consistent and useful representation of phase equilibria...... interaction parameters) in modern equations of state.In particular, the phase equilibria of binary mixtures containing CO2 and heavy n-alkanes have been studied by an important number of authors and using different types of models, achieving only partially accurate results and realizing the difficulties...... that these systems showing type III phase behavior (from C14 on) present for predicting or even correlating their phase equilibrium data in wide ranges of temperature and pressure.Cubic mixing rules (CMRs), implemented as a natural extension of the classical quadratic mixing rules, constitute the simplest...

  4. Methane mole fraction and δ13C above and below the trade wind inversion at Ascension Island in air sampled by aerial robotics

    Science.gov (United States)

    Brownlow, R.; Lowry, D.; Thomas, R. M.; Fisher, R. E.; France, J. L.; Cain, M.; Richardson, T. S.; Greatwood, C.; Freer, J.; Pyle, J. A.; MacKenzie, A. R.; Nisbet, E. G.

    2016-11-01

    Ascension Island is a remote South Atlantic equatorial site, ideal for monitoring tropical background CH4. In September 2014 and July 2015, octocopters were used to collect air samples in Tedlar bags from different heights above and below the well-defined Trade Wind Inversion (TWI), sampling a maximum altitude of 2700 m above mean sea level. Sampling captured both remote air in the marine boundary layer below the TWI and also air masses above the TWI that had been lofted by convective systems in the African tropics. Air above the TWI was characterized by higher CH4, but no distinct shift in δ13C was observed compared to the air below. Back trajectories indicate that lofted CH4 emissions from Southern Hemisphere Africa have bulk δ13CCH4 signatures similar to background, suggesting mixed emissions from wetlands, agriculture, and biomass burning. The campaigns illustrate the usefulness of unmanned aerial system sampling and Ascension's value for atmospheric measurement in an understudied region.

  5. Naked mole-rat has increased translational fidelity compared with the mouse, as well as a unique 28S ribosomal RNA cleavage.

    Science.gov (United States)

    Azpurua, Jorge; Ke, Zhonghe; Chen, Iris X; Zhang, Quanwei; Ermolenko, Dmitri N; Zhang, Zhengdong D; Gorbunova, Vera; Seluanov, Andrei

    2013-10-22

    The naked mole-rat (Heterocephalus glaber) is a subterranean eusocial rodent with a markedly long lifespan and resistance to tumorigenesis. Multiple data implicate modulation of protein translation in longevity. Here we report that 28S ribosomal RNA (rRNA) of the naked mole-rat is processed into two smaller fragments of unequal size. The two breakpoints are located in the 28S rRNA divergent region 6 and excise a fragment of 263 nt. The excised fragment is unique to the naked mole-rat rRNA and does not show homology to other genomic regions. Because this hidden break site could alter ribosome structure, we investigated whether translation rate and amino acid incorporation fidelity were altered. We report that naked mole-rat fibroblasts have significantly increased translational fidelity despite having comparable translation rates with mouse fibroblasts. Although we cannot directly test whether the unique 28S rRNA structure contributes to the increased fidelity of translation, we speculate that it may change the folding or dynamics of the large ribosomal subunit, altering the rate of GTP hydrolysis and/or interaction of the large subunit with tRNA during accommodation, thus affecting the fidelity of protein synthesis. In summary, our results show that naked mole-rat cells produce fewer aberrant proteins, supporting the hypothesis that the more stable proteome of the naked mole-rat contributes to its longevity.

  6. Series expansion in fractional calculus and fractional differential equations

    OpenAIRE

    Li, Ming-Fan; Ren, Ji-Rong; Zhu, Tao

    2009-01-01

    Fractional calculus is the calculus of differentiation and integration of non-integer orders. In a recently paper (Annals of Physics 323 (2008) 2756-2778), the Fundamental Theorem of Fractional Calculus is highlighted. Based on this theorem, in this paper we introduce fractional series expansion method to fractional calculus. We define a kind of fractional Taylor series of an infinitely fractionally-differentiable function. Further, based on our definition we generalize hypergeometric functio...

  7. Fractional calculus in pharmacokinetics.

    Science.gov (United States)

    Sopasakis, Pantelis; Sarimveis, Haralambos; Macheras, Panos; Dokoumetzidis, Aristides

    2018-02-01

    We are witnessing the birth of a new variety of pharmacokinetics where non-integer-order differential equations are employed to study the time course of drugs in the body: this is dubbed "fractional pharmacokinetics". The presence of fractional kinetics has important clinical implications such as the lack of a half-life, observed, for example with the drug amiodarone and the associated irregular accumulation patterns following constant and multiple-dose administration. Building models that accurately reflect this behaviour is essential for the design of less toxic and more effective drug administration protocols and devices. This article introduces the readers to the theory of fractional pharmacokinetics and the research challenges that arise. After a short introduction to the concepts of fractional calculus, and the main applications that have appeared in literature up to date, we address two important aspects. First, numerical methods that allow us to simulate fractional order systems accurately and second, optimal control methodologies that can be used to design dosing regimens to individuals and populations.

  8. Determining polarity and dislocation core structures at atomic level for epitaxial AlN/(0001)6H-SiC from a single image in HRTEM.

    Science.gov (United States)

    Cui, Y X; Wang, Y M; Wen, C; Ge, B H; Li, F H; Chen, Y; Chen, H

    2013-03-01

    The polarity of epitaxial AlN film grown on (0001)6H-SiC and dislocation core structures in the film have been studied using a 200 kV LaB6 high-resolution transmission electron microscope of point resolution about 0.2 nm. A posterior image processing technique, the image deconvolution, was utilized to transform a single [21¯1¯0] image that does not intuitively represent the structure into the projected structure map. The adjacent Al and N projected atomic columns with the interatomic distance 0.109 nm can be distinguished from each other by analyzing the image contrast change with the sample thickness based on the pseudo-weak phase object approximation. This makes possible to derive the polarity and core structures of partial dislocations in the epitaxial AlN film at atomic level from a single image without relying on any other additional structure information. The atomic configurations for two partial dislocations containing a 10-atom ring and a 12-atom ring, respectively, have been attained. The method is available for II-VI and other III-V compounds. Its principle and procedure are briefly introduced. Copyright © 2012 Elsevier B.V. All rights reserved.

  9. Interfacial and electrical properties of Al2O3/GaN metal-oxide-semiconductor junctions with ultrathin AlN layer

    Science.gov (United States)

    Kim, Hogyoung; Kim, Dong Ha; Choi, Byung Joon

    2017-12-01

    Ultrathin AlN layer deposited by atomic layer deposition (ALD) was employed in Al2O3/GaN metal-oxide-semiconductor (MOS) capacitors, and their interfacial and electrical properties were investigated using X-ray photoelectron spectroscopy (XPS) and current-voltage ( I-V) and capacitance-voltage ( C-V) measurements. XPS analyses revealed that the diffusion of N atoms into Al2O3 and the degradation of Al2O3 film quality were significant for the thickest Al2O3 (10 nm). The sample with a 10-nm-thick Al2O3 layer produced the highest leakage current and trap density. These results may result from the deteriorated interface characteristics near the AlN layer caused by long growth time. Therefore, it is suggested that the Al2O3 thickness (and optimal growth time) is a key factor in Al2O3/AlN/GaN MOS capacitors.

  10. Influence of Surface Passivation on AlN Barrier Stress and Scattering Mechanism in Ultra-thin AlN/GaN Heterostructure Field-Effect Transistors

    Science.gov (United States)

    Lv, Y. J.; Song, X. B.; Wang, Y. G.; Fang, Y. L.; Feng, Z. H.

    2016-08-01

    Ultra-thin AlN/GaN heterostructure field-effect transistors (HFETs) with, and without, SiN passivation were fabricated by the same growth and device processes. Based on the measured DC characteristics, including the capacitance-voltage ( C- V) and output current-voltage ( I- V) curves, the variation of electron mobility with gate bias was found to be quite different for devices with, and without, SiN passivation. Although the AlN barrier layer is ultra thin ( c. 3 nm), it was proved that SiN passivation induces no additional tensile stress and has no significant influence on the piezoelectric polarization of the AlN layer using Hall and Raman measurements. The SiN passivation was found to affect the surface properties, thereby increasing the electron density of the two-dimensional electron gas (2DEG) under the access region. The higher electron density in the access region after SiN passivation enhanced the electrostatic screening for the non-uniform distributed polarization charges, meaning that the polarization Coulomb field scattering has a weaker effect on the electron drift mobility in AlN/GaN-based devices.

  11. First-Principles Study on Stability and Magnetism of NimAln (m=1–3, n=1–9 Clusters

    Directory of Open Access Journals (Sweden)

    Xiao Zhang

    2013-01-01

    Full Text Available The investigation on the structures, stabilities, and magnetism of NimAln (m=1–3, n=1–9 clusters has been made by using first principles. We found some new ground-state structures which had not been found before. These mixed species prefer to adopt three-dimensional (3D structures starting from four atoms. All the ground-state structures for the Ni-Al clusters are different from those of the corresponding pure Al clusters with the same number of atoms except for three atoms. The Mulliken population analysis shows that some charges transfer from the Al atoms to the Ni atoms. NiAln (n = odd number cations, Ni2Al6 neutral, Ni2Al1 and Ni3Al cations and anions, and Ni3Al5 anion have the magnetic moments of 2 μB. The magnetic moments of NiAl4 and NiAl6 cluster neutrals and cations are 2 μB and 3 μB, respectively. All the other cluster neutrals and ions do not have any nontrivial magnetic moments. The 3d electrons in Ni atoms are mainly responsible for the magnetism of the mixed Ni-Al clusters.

  12. Metallic and/or oxygen ion implantation into AlN ceramics as a method of preparation for its direct bonding with copper

    International Nuclear Information System (INIS)

    Barlak, M.; Borkowska, K.; Olesinska, W.; Kalinski, D.; Piekoszewski, J.; Werner, Z.; Jagielski, J.; Sartowska, B.

    2006-01-01

    Direct bonding (DB) process is recently getting an increasing interest as a method for producing high quality joints between aluminum nitride (AlN) ceramics and copper. The metallic ions were implanted using an MEVVA type TITAN implanter with unseparated beam. Oxygen ions were implanted using a semi-industrial ion implanter without mass separation equipped with a gaseous ion source. The substrate temperature did not exceed 200 o C. Ions were implanted at two acceleration voltages, i.e. 15 and 70 kV. The fluence range was between 1·E16 and 1·E18 cm -2 . After implantation, some of the samples were characterized by the Rutherford backscattering (RBS) method. In conclusion: (a) The investigations performed in the present work confirm an assumption that ion implantation is a very promising technique as a pretreatment of AlN ceramics for the formation of the joints with copper in direct bonding process. (b) It has been shown that titanium implantation gives the best results in comparison to other metals examined (Fe, Cr, Cu) but also in comparison to double Ti+O and O+Ti implantations

  13. Structural properties of Al{sub 2}O{sub 3}/AlN thin film prepared by magnetron sputtering of Al in HF-activated nitrogen plasma

    Energy Technology Data Exchange (ETDEWEB)

    Dallaeva, D.S. [Dagestan State Technical University, av. I. Shamilya 70a, Machachkala, 367015 Dagestan Republic (Russian Federation); Dagestan State University, M. Gadgieva street, Machachkala, 367001 Dagestan Republic (Russian Federation); Brno University of Technology, Faculty of Electrical Engineering and Communication, Physics Department, Technicka 8, 616 00 Brno (Czech Republic); Bilalov, B.A.; Gitikchiev, M.A.; Kardashova, G.D.; Safaraliev, G.K. [Dagestan State Technical University, av. I. Shamilya 70a, Machachkala, 367015 Dagestan Republic (Russian Federation); Dagestan State University, M. Gadgieva street, Machachkala, 367001 Dagestan Republic (Russian Federation); Tomanek, P., E-mail: tomanek@feec.vutbr.cz [Brno University of Technology, Faculty of Electrical Engineering and Communication, Physics Department, Technicka 8, 616 00 Brno (Czech Republic); Skarvada, P. [Brno University of Technology, Faculty of Electrical Engineering and Communication, Physics Department, Technicka 8, 616 00 Brno (Czech Republic); Smith, S. [South Dakota School of Mines and Technology, Physics Department, 501 E. St. Joseph St, Rapid City, SD 57701 (United States)

    2012-12-30

    A process for ion-plasma formation of aluminum nitride (AlN) nanolayers on nitrided sapphire (Al{sub 2}O{sub 3}) substrates is presented. The method is based on the direct current magnetron sputtering of a high-purity aluminum target in the presence of an argon-nitrogen gas mix and high frequency-activated nitrogen plasma. The method, combined with ion etching, produced matched layers by nitration of Al{sub 2}O{sub 3} in the (0001) plane, and formation of high quality AlN epilayers on this surface was observed. The processing characteristics and morphology dependence on synthesis parameters were studied using atomic force microscopy. - Highlights: Black-Right-Pointing-Pointer Technology based on plasma processes was used. Black-Right-Pointing-Pointer Shemical composition of elements in the layers was analyzed. Black-Right-Pointing-Pointer Near-surface layer was obtained on the sapphire substrate by nitridation. Black-Right-Pointing-Pointer Increasing of substrate temperature stimulates the growth of layer perfection. Black-Right-Pointing-Pointer Morphology is connected with growth mechanism and the structure of substrate.

  14. Evaluation of the influence of GaN and AlN as pseudosubstrates on the crystalline quality of InN layers

    Energy Technology Data Exchange (ETDEWEB)

    Lozano, J.G.; Morales, F.M.; Garcia, R.; Gonzalez, D. [Departamento de Ciencia de los Materiales e Ingenieria Metalurgica y Quimica Inorganica, Universidad de Cadiz, Apartado 40, 11510, Puerto Real, Cadiz (Spain); Lebedev, V.; Cimalla, V.; Ambacher, O. [Center for Micro- and Nanotechnologies, Technical University Ilmenau, 98684 Ilmenau (Germany)

    2007-04-15

    A study of the impact of different pseudosubstrates as AlN, GaN or AlN/GaN on the crystalline quality of InN layers by transmission electron microscopy is reported. The temperature of the substrate was found to play an important role: for higher temperatures, low quality InN layers are obtained, poorly supported on the buffers and consequently almost free of dislocations; whereas for lower temperatures, higher qualities, with smooth surfaces and continuous interfaces are observed. In these cases, high resolution electron microscopy showed that the high lattice mismatch existing between the pseudosubstrate and the InN epilayer is mainly accommodated by a network of geometrical misfit dislocations at the heterointerface. Additionally, low densities of threading dislocations, also decaying exponentially with the increasing thickness were observed. The introduction of a GaN buffer layer on top of AlN promotes the reduction in one order of magnitude the density of threading dislocations in the epilayer, partially due to the reduction of dislocations propagating from the pseudosubstrate. However, other relevant factors as the domains coalescence or the generation of secondary misfit dislocation must be taken into account. (copyright 2007 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  15. AlN Surface Passivation of GaN-Based High Electron Mobility Transistors by Plasma-Enhanced Atomic Layer Deposition

    Science.gov (United States)

    Tzou, An-Jye; Chu, Kuo-Hsiung; Lin, I.-Feng; Østreng, Erik; Fang, Yung-Sheng; Wu, Xiao-Peng; Wu, Bo-Wei; Shen, Chang-Hong; Shieh, Jia-Ming; Yeh, Wen-Kuan; Chang, Chun-Yen; Kuo, Hao-Chung

    2017-04-01

    We report a low current collapse GaN-based high electron mobility transistor (HEMT) with an excellent thermal stability at 150 °C. The AlN was grown by N2-based plasma enhanced atomic layer deposition (PEALD) and shown a refractive index of 1.94 at 633 nm of wavelength. Prior to deposit AlN on III-nitrides, the H2/NH3 plasma pre-treatment led to remove the native gallium oxide. The X-ray photoelectron spectroscopy (XPS) spectroscopy confirmed that the native oxide can be effectively decomposed by hydrogen plasma. Following the in situ ALD-AlN passivation, the surface traps can be eliminated and corresponding to a 22.1% of current collapse with quiescent drain bias ( V DSQ) at 40 V. Furthermore, the high temperature measurement exhibited a shift-free threshold voltage ( V th), corresponding to a 40.2% of current collapse at 150 °C. The thermal stable HEMT enabled a breakdown voltage (BV) to 687 V at high temperature, promising a good thermal reliability under high power operation.

  16. FRACTIONS: CONCEPTUAL AND DIDACTIC ASPECTS

    OpenAIRE

    Sead Rešić; Ismet Botonjić; Maid Omerović

    2016-01-01

    Fractions represent the manner of writing parts of whole numbers (integers). Rules for operations with fractions differ from rules for operations with integers. Students face difficulties in understanding fractions, especially operations with fractions. These difficulties are well known in didactics of Mathematics throughout the world and there is a lot of research regarding problems in learning about fractions. Methods for facilitating understanding fractions have been discovered...

  17. Fractional-order devices

    CERN Document Server

    Biswas, Karabi; Caponetto, Riccardo; Mendes Lopes, António; Tenreiro Machado, José António

    2017-01-01

    This book focuses on two specific areas related to fractional order systems – the realization of physical devices characterized by non-integer order impedance, usually called fractional-order elements (FOEs); and the characterization of vegetable tissues via electrical impedance spectroscopy (EIS) – and provides readers with new tools for designing new types of integrated circuits. The majority of the book addresses FOEs. The interest in these topics is related to the need to produce “analogue” electronic devices characterized by non-integer order impedance, and to the characterization of natural phenomena, which are systems with memory or aftereffects and for which the fractional-order calculus tool is the ideal choice for analysis. FOEs represent the building blocks for designing and realizing analogue integrated electronic circuits, which the authors believe hold the potential for a wealth of mass-market applications. The freedom to choose either an integer- or non-integer-order analogue integrator...

  18. FRACTIONAL CRYSTALLIZATION FEED ENVELOPE

    International Nuclear Information System (INIS)

    HERTING DL

    2008-01-01

    Laboratory work was completed on a set of evaporation tests designed to establish a feed envelope for the fractional crystallization process. The feed envelope defines chemical concentration limits within which the process can be operated successfully. All 38 runs in the half-factorial design matrix were completed successfully, based on the qualitative definition of success. There is no feed composition likely to be derived from saltcake dissolution that would cause the fractional crystallization process to not meet acceptable performance requirements. However, some compositions clearly would provide more successful operation than other compositions

  19. Social status and sex independently influence androgen receptor expression in the eusocial naked mole-rat brain.

    Science.gov (United States)

    Holmes, Melissa M; Goldman, Bruce D; Forger, Nancy G

    2008-08-01

    Naked mole-rats (Heterocephalus glaber) are eusocial rodents that live in large subterranean colonies including a single breeding female and 1-3 breeding males; all other members of the colony, known as subordinates, are reproductively suppressed. We recently found that naked mole-rats lack many of the sex differences in the brain and spinal cord commonly found in other rodents. Instead, neural morphology is influenced by breeding status, such that breeders, regardless of sex, have more neurons than subordinates in the ventromedial nucleus of the hypothalamus (VMH), and larger overall volumes of the bed nucleus of the stria terminalis (BST), paraventricular nucleus (PVN) and medial amygdala (MeA). To begin to understand how breeding status influences brain morphology, we examined the distribution of androgen receptor (AR) immunoreactivity in gonadally intact breeders and subordinates of both sexes. All animals had AR+ nuclei in many of the same regions positive for AR in other mammals, including the VMH, BST, PVN, MeA, and the ventral portion of the premammillary nucleus (PMv). We also observed diffuse labeling throughout the preoptic area, demonstrating that distribution of the AR protein in presumptive reproductive brain nuclei is well-conserved, even in a species that exhibits remarkably little sexual dimorphism. In contrast to other rodents, however, naked mole-rats lacked AR+ nuclei in the suprachiasmatic nucleus and hippocampus. Males had more AR+ nuclei in the MeA, VMH, and PMv than did females. Surprisingly, breeders had significantly fewer AR+ nuclei than subordinates in all brain regions examined (VMH, BST, PVN, MeA, and PMv). Thus, social status is strongly correlated with AR immunoreactivity in this eusocial species.

  20. Postprandial heat increment does not substitute for active thermogenesis in cold-challenged star-nosed moles (Condylura cristata).

    Science.gov (United States)

    Campbell, K L; McIntyre, I W; MacArthur, R A

    2000-01-01

    The postprandial increase in metabolic rate associated with consuming, assimilating and excreting a meal is often termed the heat increment of feeding (HIF). The metabolic heat production of star-nosed moles, Condylura cristata, held at thermoneutrality was monitored for 4 h following a single 10 min session of feeding on a ration consisting of 0 g (controls), 3.5 g or 10 g of earthworms. Coefficients for metabolizable energy digestibility and digesta passage rate of earthworms fed to C. cristata were also determined. We then tested whether feeding-induced thermogenesis substitutes partially or completely for thermoregulatory heat production in these animals exposed to sub-thermoneutral air temperatures (9-24 degrees C). A single feeding on earthworms had both short- and long-term effects on the metabolic rate and respiratory exchange ratio of C. cristata. The observed short-term (0-65 min) rise in metabolic rate, assumed to be associated primarily with the physical costs of nutrient digestion, absorption and excretion, was similar to the calculated mean retention time (66.7+/-7.8 min; mean +/- s.e. m., N=5) of this species. This component of the HIF represented 2.9 % of the food energy ingested by moles fed a single 3.5 g (13.21 kJ) meal of earthworms and 1.4 % of the food energy ingested by moles fed a single 7.5 g (28.09 kJ) meal of earthworms. At all test temperatures, resting metabolic rate typically remained above fasting levels for 1-4 h following ingestion of the high-protein earthworm diet. This protracted rise in metabolic rate, presumably associated with the biochemical costs of amino acid oxidation/gluconeogenesis and ureagenesis, averaged 12.8 % of the metabolizable energy and 8.7 % of the gross energy intake. Despite the potential thermoregulatory benefit, we found no evidence that biochemical HIF substitutes for facultative thermogenesis in star-nosed moles exposed to low air temperatures.

  1. EQUATION OF STATE IN FORM WHICH RELATES MOL FRACTION AND MOLARITY OF TWO (OR MORE COMPONENT THERMODYNAMIC SYSTEM CONSISTED OF IDEAL GASES, AND IT'S APPLICATIONS

    Directory of Open Access Journals (Sweden)

    Marko Popović

    2010-01-01

    Full Text Available Most people would face a problem if there is a need to calculate the mole fraction of a substance A in a gaseous solution (a thermodynamic system containing two or more ideal gases knowing its molarity at a given temperature and pressure. For most it would take a lot of time and calculations to find the answer, especially because the quantities of other substances in the system aren't given. An even greater problem arises when we try to understand how special relativity affects gaseous systems, especially solutions and systems in equilibrium. In this paper formulas are suggested that greatly shorten the process of conversion from molarity to mole fraction and give us a better insight into the relativistic effects on a gaseous system.

  2. Sweet Work with Fractions

    Science.gov (United States)

    Vinogradova, Natalya; Blaine, Larry

    2013-01-01

    Almost everyone loves chocolate. However, the same cannot be said about fractions, which are loved by markedly fewer. Middle school students tend to view them with wary respect, but little affection. The authors attempt to sweeten the subject by describing a type of game involving division of chocolate bars. The activity they describe provides a…

  3. Fractional Differential Equation

    Directory of Open Access Journals (Sweden)

    Moustafa El-Shahed

    2007-01-01

    where 2<α<3 is a real number and D0+α is the standard Riemann-Liouville fractional derivative. Our analysis relies on Krasnoselskiis fixed point theorem of cone preserving operators. An example is also given to illustrate the main results.

  4. Nonlinear fractional relaxation

    Indian Academy of Sciences (India)

    Abstract. We define a nonlinear model for fractional relaxation phenomena. We use ε-expansion method to analyse this model. By studying the fundamental solutions of this model we find that when t → 0 the model exhibits a fast decay rate and when t → ∞ the model exhibits a power-law decay. By analysing the frequency ...

  5. Vapor liquid fraction determination

    International Nuclear Information System (INIS)

    1980-01-01

    This invention describes a method of measuring liquid and vapor fractions in a non-homogeneous fluid flowing through an elongate conduit, such as may be required with boiling water, non-boiling turbulent flows, fluidized bed experiments, water-gas mixing analysis, and nuclear plant cooling. (UK)

  6. Brewing with fractionated barley

    NARCIS (Netherlands)

    Donkelaar, van L.H.G.

    2016-01-01

    Brewing with fractionated barley

    Beer is a globally consumed beverage, which is produced from malted barley, water, hops and yeast. In recent years, the use of unmalted barley and exogenous enzymes have become more popular because they enable simpler processing and reduced environmental

  7. Fermion Number Fractionization

    Indian Academy of Sciences (India)

    Home; Journals; Resonance – Journal of Science Education; Volume 13; Issue 8. Fermion Number Fractionization. Kumar Rao Narendra Sahu Prasanta K ... Author Affiliations. Kumar Rao1 Narendra Sahu1 Prasanta K Panigrahi1. Theoretical Physics Division, Physical Research Laboratory, Ahmedabad 380 009, India ...

  8. Brewing with fractionated barley

    NARCIS (Netherlands)

    Donkelaar, van L.H.G.

    2016-01-01

    Brewing with fractionated barley Beer is a globally consumed beverage, which is produced from malted barley, water, hops and yeast. In recent years, the use of unmalted barley and exogenous enzymes have become more popular because they enable simpler processing and reduced environmental impact. Raw

  9. Selective area growth of AlN/GaN nanocolumns on (0001) and (11-22) GaN/sapphire for semi-polar and non-polar AlN pseudo-templates

    Science.gov (United States)

    Bengoechea-Encabo, A.; Albert, S.; Müller, M.; Xie, M.–Y.; Veit, P.; Bertram, F.; Sanchez-Garcia, M. A.; Zúñiga-Pérez, J.; de Mierry, P.; Christen, J.; Calleja, E.

    2017-09-01

    Despite the strong interest in optoelectronic devices working in the deep ultraviolet range, no suitable low cost, large-area, high-quality AlN substrates have been available up to now. The aim of this work is the selective area growth of AlN nanocolumns by plasma assisted molecular beam epitaxy on polar (0001) and semi-polar (11-22) GaN/sapphire templates. The resulting AlN nanocolumns are vertically oriented with semi-polar {1-103} top facets when grown on (0001) GaN/sapphire, or oriented at 58° from the template normal and exposing {1-100} non-polar top facets when growing on (11-22) GaN/sapphire, in both cases reaching filling factors ≥80%. In these kinds of arrays each nanostructure could function as a building block for an individual nano-device or, due to the large filling factor values, the overall array top surfaces could be seen as a quasi (semi-polar or non-polar) AlN pseudo-template.

  10. Thujone-Rich Fraction of Thuja occidentalis Demonstrates Major Anti-Cancer Potentials: Evidences from In Vitro Studies on A375 Cells

    OpenAIRE

    Biswas, Raktim; Mandal, Sushil Kumar; Dutta, Suman; Bhattacharyya, Soumya Sundar; Boujedaini, Naoual; Khuda-Bukhsh, Anisur Rahman

    2011-01-01

    Crude ethanolic extract of Thuja occidentalis (Fam: Cupressaceae) is used as homeopathic mother tincture (TOΦ) to treat various ailments, particularly moles and tumors, and also used in various other systems of traditional medicine. Anti-proliferative and apoptosis-inducing properties of TOΦ and the thujone-rich fraction (TRF) separated from it have been evaluated for their possible anti-cancer potentials in the malignant melanoma cell line A375. On initial trial by S-diphenyltetrazolium brom...

  11. Transcriptome sequencing of the blind subterranean mole rat, Spalax galili: utility and potential for the discovery of novel evolutionary patterns.

    Directory of Open Access Journals (Sweden)

    Assaf Malik

    Full Text Available The blind subterranean mole rat (Spalax ehrenbergi superspecies is a model animal for survival under extreme environments due to its ability to live in underground habitats under severe hypoxic stress and darkness. Here we report the transcriptome sequencing of Spalax galili, a chromosomal type of S. ehrenbergi. cDNA pools from muscle and brain tissues isolated from animals exposed to hypoxic and normoxic conditions were sequenced using Sanger, GS FLX, and GS FLX Titanium technologies. Assembly of the sequences yielded over 51,000 isotigs with homology to ∼12,000 mouse, rat or human genes. Based on these results, it was possible to detect large numbers of splice variants, SNPs, and novel transcribed regions. In addition, multiple differential expression patterns were detected between tissues and treatments. The results presented here will serve as a valuable resource for future studies aimed at identifying genes and gene regions evolved during the adaptive radiation associated with underground life of the blind mole rat.

  12. Evaluation on Morphological Characters of European Mole cricket, Gryllotalpa gryllotalpa (Orth.: Gryllotalpidae in the North-west of Iran

    Directory of Open Access Journals (Sweden)

    M.H. Kazemi

    2011-06-01

    Full Text Available The European mole cricket is considered to be of the most important insect pests of Iran, especially in Azerbaijan province. Its damage in some area economically is very high. In this study, morphological characteristics, including the length of various parts of the pest body, were evaluated. Analyzing of the size of fore and hind wings results of the adults in this species, showed that there were seasonal dimorphism as long-winged (L.W. and short-winged (S.W. among the insects. Based on the literature available seasonal dimorphism in this species is the first report in the world, and probably each morph of this species is various in different both in the biology and behavior. Sexual dimorphism can be distinguished by study pattern of venation in the forewings of sexes. One of the important characteristics in distinguishing mole cricket species is arrangement spines in the fore and hind tibia where their numbers and sizes of these spines in various species are different. The fore tibia of insect has four wide and strong dactyls in its apex, but lateral margin of the hind tibia armed with five sharp spines with seven spines at the end of its tibia.

  13. The anti-tumorigenic activity of A2M-A lesson from the naked mole-rat.

    Directory of Open Access Journals (Sweden)

    Susanne Kurz

    Full Text Available Cancer resistance is a major cause for longevity of the naked mole-rat. Recent liver transcriptome analysis in this animal compared to wild-derived mice revealed higher expression of alpha2-macroglobulin (A2M and cell adhesion molecules, which contribute to the naked mole-rat's cancer resistance. Notably, A2M is known to dramatically decrease with age in humans. We hypothesize that this might facilitate tumour development. Here we found that A2M modulates tumour cell adhesion, migration and growth by inhibition of tumour promoting signalling pathways, e.g. PI3K / AKT, SMAD and up-regulated PTEN via down-regulation of miR-21, in vitro and in tumour xenografts. A2M increases the expression of CD29 and CD44 but did not evoke EMT. Transcriptome analysis of A2M-treated tumour cells, xenografts and mouse liver demonstrated a multifaceted regulation of tumour promoting signalling pathways indicating a less tumorigenic environment mediated by A2M. By virtue of these multiple actions the naturally occurring A2M has strong potential as a novel therapeutic agent.

  14. The anti-tumorigenic activity of A2M-A lesson from the naked mole-rat.

    Science.gov (United States)

    Kurz, Susanne; Thieme, René; Amberg, Ronny; Groth, Marco; Jahnke, Heinz-Georg; Pieroh, Philipp; Horn, Lars-Christian; Kolb, Marlen; Huse, Klaus; Platzer, Matthias; Volke, Daniela; Dehghani, Faramarz; Buzdin, Anton; Engel, Kathrin; Robitzki, Andrea; Hoffmann, Ralf; Gockel, Ines; Birkenmeier, Gerd

    2017-01-01

    Cancer resistance is a major cause for longevity of the naked mole-rat. Recent liver transcriptome analysis in this animal compared to wild-derived mice revealed higher expression of alpha2-macroglobulin (A2M) and cell adhesion molecules, which contribute to the naked mole-rat's cancer resistance. Notably, A2M is known to dramatically decrease with age in humans. We hypothesize that this might facilitate tumour development. Here we found that A2M modulates tumour cell adhesion, migration and growth by inhibition of tumour promoting signalling pathways, e.g. PI3K / AKT, SMAD and up-regulated PTEN via down-regulation of miR-21, in vitro and in tumour xenografts. A2M increases the expression of CD29 and CD44 but did not evoke EMT. Transcriptome analysis of A2M-treated tumour cells, xenografts and mouse liver demonstrated a multifaceted regulation of tumour promoting signalling pathways indicating a less tumorigenic environment mediated by A2M. By virtue of these multiple actions the naturally occurring A2M has strong potential as a novel therapeutic agent.

  15. Negligible senescence in the longest living rodent, the naked mole-rat: insights from a successfully aging species.

    Science.gov (United States)

    Buffenstein, Rochelle

    2008-05-01

    Aging refers to a gradual deterioration in function that, over time, leads to increased mortality risk, and declining fertility. This pervasive process occurs in almost all organisms, although some long-lived trees and cold water inhabitants reportedly show insignificant aging. Negligible senescence is characterized by attenuated age-related change in reproductive and physiological functions, as well as no observable age-related gradual increase in mortality rate. It was questioned whether the longest living rodent, the naked mole-rat, met these three strict criteria. Naked mole-rats live in captivity for more than 28.3 years, approximately 9 times longer than similar-sized mice. They maintain body composition from 2 to 24 years, and show only slight age-related changes in all physiological and morphological characteristics studied to date. Surprisingly breeding females show no decline in fertility even when well into their third decade of life. Moreover, these animals have never been observed to develop any spontaneous neoplasm. As such they do not show the typical age-associated acceleration in mortality risk that characterizes every other known mammalian species and may therefore be the first reported mammal showing negligible senescence over the majority of their long lifespan. Clearly physiological and biochemical processes in this species have evolved to dramatically extend healthy lifespan. The challenge that lies ahead is to understand what these mechanisms are.

  16. Walking the oxidative stress tightrope: a perspective from the naked mole-rat, the longest-living rodent.

    Science.gov (United States)

    Rodriguez, Karl A; Wywial, Ewa; Perez, Viviana I; Lambert, Adriant J; Edrey, Yael H; Lewis, Kaitlyn N; Grimes, Kelly; Lindsey, Merry L; Brand, Martin D; Buffenstein, Rochelle

    2011-01-01

    Reactive oxygen species (ROS), by-products of aerobic metabolism, cause oxidative damage to cells and tissue and not surprisingly many theories have arisen to link ROS-induced oxidative stress to aging and health. While studies clearly link ROS to a plethora of divergent diseases, their role in aging is still debatable. Genetic knock-down manipulations of antioxidants alter the levels of accrued oxidative damage, however, the resultant effect of increased oxidative stress on lifespan are equivocal. Similarly the impact of elevating antioxidant levels through transgenic manipulations yield inconsistent effects on longevity. Furthermore, comparative data from a wide range of endotherms with disparate longevity remain inconclusive. Many long-living species such as birds, bats and mole-rats exhibit high-levels of oxidative damage, evident already at young ages. Clearly, neither the amount of ROS per se nor the sensitivity in neutralizing ROS are as important as whether or not the accrued oxidative stress leads to oxidative-damage-linked age-associated diseases. In this review we examine the literature on ROS, its relation to disease and the lessons gleaned from a comparative approach based upon species with widely divergent responses. We specifically focus on the longest lived rodent, the naked mole-rat, which maintains good health and provides novel insights into the paradox of maintaining both an extended healthspan and lifespan despite high oxidative stress from a young age.

  17. Transcriptome sequencing of the blind subterranean mole rat, Spalax galili: Utility and potential for the discovery of novel evolutionary patterns

    KAUST Repository

    Malik, Assaf

    2011-08-12

    The blind subterranean mole rat (Spalax ehrenbergi superspecies) is a model animal for survival under extreme environments due to its ability to live in underground habitats under severe hypoxic stress and darkness. Here we report the transcriptome sequencing of Spalax galili, a chromosomal type of S. ehrenbergi. cDNA pools from muscle and brain tissues isolated from animals exposed to hypoxic and normoxic conditions were sequenced using Sanger, GS FLX, and GS FLX Titanium technologies. Assembly of the sequences yielded over 51,000 isotigs with homology to ~12,000 mouse, rat or human genes. Based on these results, it was possible to detect large numbers of splice variants, SNPs, and novel transcribed regions. In addition, multiple differential expression patterns were detected between tissues and treatments. The results presented here will serve as a valuable resource for future studies aimed at identifying genes and gene regions evolved during the adaptive radiation associated with underground life of the blind mole rat. 2011 Malik et al.

  18. Fractional Poisson Fields and Martingales

    Science.gov (United States)

    Aletti, Giacomo; Leonenko, Nikolai; Merzbach, Ely

    2018-01-01

    We present new properties for the Fractional Poisson process (FPP) and the Fractional Poisson field on the plane. A martingale characterization for FPPs is given. We extend this result to Fractional Poisson fields, obtaining some other characterizations. The fractional differential equations are studied. We consider a more general Mixed-Fractional Poisson process and show that this process is the stochastic solution of a system of fractional differential-difference equations. Finally, we give some simulations of the Fractional Poisson field on the plane.

  19. Fractional Poisson Fields and Martingales

    Science.gov (United States)

    Aletti, Giacomo; Leonenko, Nikolai; Merzbach, Ely

    2018-02-01

    We present new properties for the Fractional Poisson process (FPP) and the Fractional Poisson field on the plane. A martingale characterization for FPPs is given. We extend this result to Fractional Poisson fields, obtaining some other characterizations. The fractional differential equations are studied. We consider a more general Mixed-Fractional Poisson process and show that this process is the stochastic solution of a system of fractional differential-difference equations. Finally, we give some simulations of the Fractional Poisson field on the plane.

  20. -Dimensional Fractional Lagrange's Inversion Theorem

    Directory of Open Access Journals (Sweden)

    F. A. Abd El-Salam

    2013-01-01

    Full Text Available Using Riemann-Liouville fractional differential operator, a fractional extension of the Lagrange inversion theorem and related formulas are developed. The required basic definitions, lemmas, and theorems in the fractional calculus are presented. A fractional form of Lagrange's expansion for one implicitly defined independent variable is obtained. Then, a fractional version of Lagrange's expansion in more than one unknown function is generalized. For extending the treatment in higher dimensions, some relevant vectors and tensors definitions and notations are presented. A fractional Taylor expansion of a function of -dimensional polyadics is derived. A fractional -dimensional Lagrange inversion theorem is proved.