bluuebunny/crossref_metadata_2025 huggingface dataset:
The Reemergence of Slovakia
Authors: Ramet Sabrina Petra
Published: September 2011

There are no differences between the Czech and Slovak governments’ views on the forms of the future coexistence and relations between the Czech Republic and the Slovak Republic. Our positions are literally identical.

Vladimir Meciar, Prime Minister of the Slovak Republic (August 1990)

Since our democratic revolution, the situation [in relations between the Czech Republic and the Slovak Republic] has never been as serious and precipitous as it is today.

Vaclav Havel, President of the Czech and Slovak Federative Republic (September 1991)

On 9 June 1992 came the shattering announcement by newly elected Czech Republic Prime Minister Vaclav Klaus, that the Czechoslovak federation was no more. An interim (but trimmed) federal government was to be set up to preside over the hasty dismantlement of the 74-year old state. By 30 September, the Czechoslovak Republic was to be completely split in two. And by January 1993, the finances of state are supposed to be completely divided.
The Foreign Policy Debate in Russia: In Search of a National Interest
Authors: Jonson Lena
Published: September 2011

Russia is at present seeking to define its national interest. A new foreign policy is in the process of being formed; in a debate that has run wild, the points of reference used when formulating foreign policy in the days of Soviet Marxism have been abandoned and replaced by notions about “the Russian national interest” (Rahr 1992; Crow 1992).
Soviet Emigration Since 1985
Authors: Heitman Sidney
Published: September 2011

Since the end of World War II more than one million citizens of the USSR have emigrated to the West in a unique and unprecedented movement today called the “Third Soviet Emigration.” In contrast to two earlier flights of refugees from the Revolution and from World War II, the Third Emigration is a voluntary, legally-sanctioned process involving mainly three nationalities—Jews, ethnic Germans, and Armenians. The origin of the exodus goes back to the early postwar years, but the vast majority of the emigrants have left since 1971, when the Soviet government relaxed its historic antipathy to free movement by its citizens.
Monetary Policy and Banking
Authors: Kallas Siim
Published: September 2011

Banking in Estonia Before 1992

Under the Soviet regime Estonian banking, like banking anywhere in the Soviet Union, was controlled and managed by the Central Bank of the Soviet Union. Besides the central bank, there was a limited number of all-Union banking structures with their numerous local branches in Estonia as well as in other Soviet republics. The whole banking system was state-owned and rigidly controlled from the center.
On the Fringes of Center: Disputed Hagiographic Imagery and the Crisis over theBeati moderniin Rome ca. 1600*
Authors: Noyes Ruth S.
Published: September 2011

This article sets forth, through a small collection of case studies, the extent to which the literal and pictorial figures of theBeati moderniconstituted potentially provocative and disputed hermeneutical territory between particular religious constituencies, in this case the Oratorians and the Jesuits, and an increasingly stringent Curia ca. 1600. A reexamination ofBeati modernihagiographic imagery, and curial censorship of such imagery, potentially problematizes scholarly assumptions that these images served the Counter-Reformation Church's demands to control the meaning of religious images and the cult of the saints. Such reassessment calls for the reevaluation of a newly-constituted, uniquely post-Tridentine genre of hagiographic imagery: theBeati modernidevotional altar image and its reproductive printed devotional derivatives.
β3 Integrin–EGF receptor cross-talk activates p190RhoGAP in mouse mammary gland epithelial cells
Authors: Balanis Nikolas , Yoshigi Masaaki , Wendt Michael K. , Schiemann William P. , Carlin Cathleen R.
Published: September 2011

Active RhoA localizes to plasma membrane, where it stimulates formation of focal adhesions and stress fibers. RhoA activity is inhibited by p190RhoGAP following integrin-mediated cell attachment to allow sampling of new adhesive environments. p190RhoGAP is itself activated by Src-dependent tyrosine phosphorylation, which facilitates complex formation with p120RasGAP. This complex then translocates to the cell surface, where p190RhoGAP down-regulates RhoA. Here we demonstrate that the epidermal growth factor receptor (EGFR) cooperates with β3 integrin to regulate p190RhoGAP activity in mouse mammary gland epithelial cells. Adhesion to fibronectin stimulates tyrosine phosphorylation of the EGFR in the absence of receptor ligands. Use of a dominant inhibitory EGFR mutant demonstrates that fibronectin-activated EGFR recruits p120RasGAP to the cell periphery. Expression of an inactive β3 integrin subunit abolishes p190RhoGAP tyrosine phosphorylation, demonstrating a mechanistic link between β3 integrin–activated Src and EGFR regulation of the RhoA inhibitor. The β3 integrin/EGFR pathway also has a positive role in formation of filopodia. Together our data suggest that EGFR constitutes an important intrinsic migratory cue since fibronectin is a key component of the microenvironment in normal mammary gland development and breast cancer. Our data also suggest that EGFR expressed at high levels has a role in eliciting cell shape changes associated with epithelial-to-mesenchymal transition.
Defining pathways of spindle checkpoint silencing: functional redundancy between Cdc20 ubiquitination and p31comet
Authors: Jia Luying , Li Bing , Warrington Ross T. , Hao Xing , Wang Shixuan , Yu Hongtao
Published: September 2011

The spindle checkpoint senses unattached or improperly attached kinetochores during mitosis, inhibits the anaphase-promoting complex or cyclosome (APC/C), and delays anaphase onset to prevent aneuploidy. The mitotic checkpoint complex (MCC) consisting of BubR1, Bub3, Mad2, and Cdc20 is a critical APC/C-inhibitory checkpoint complex in human cells. At the metaphase–anaphase transition, the spindle checkpoint turns off, and MCC disassembles to allow anaphase onset. The molecular mechanisms of checkpoint inactivation are poorly understood. A major unresolved issue is the role of Cdc20 autoubiquitination in this process. Although Cdc20 autoubiquitination can promote Mad2 dissociation from Cdc20, a nonubiquitinatable Cdc20 mutant still dissociates from Mad2 during checkpoint inactivation. Here, we show that depletion of p31comet delays Mad2 dissociation from Cdc20 mutants that cannot undergo autoubiquitination. Thus both p31comet and ubiquitination of Cdc20 are critical mechanisms of checkpoint inactivation. They act redundantly to promote Mad2 dissociation from Cdc20.
Finding the dimension of slow dynamics in a rhythmic system
Authors: Revzen Shai , Guckenheimer John M.
Published: September 2011

Dynamical systems with asymptotically stable periodic orbits are generic models for rhythmic processes in dissipative physical systems. This paper presents a method for reconstructing the dynamics near a periodic orbit from multivariate time-series data. It is used to test theories about the control of legged locomotion, a context in which time series are short when compared with previous work in nonlinear time-series analysis. The method presented here identifies appropriate dimensions of reduced order models for the deterministic portion of the dynamics. The paper also addresses challenges inherent in identifying dynamical models with data from different individuals.
Effects of ecohydrological variables on current and future ranges, local suitability patterns, and model accuracy in big sagebrush
Authors: Schlaepfer Daniel R. , Lauenroth William K. , Bradford John B.
Published: September 2011

Forecasting of species and ecosystem responses to novel conditions, including climate change, is one of the major challenges facing ecologists at the start of the 21st century. Climate change studies based on species distribution models (SDMs) have been criticized because they extend correlational relationships beyond the observed data. Here, we compared conventional climate‐based SDMs against ecohydrological SDMs that include information from process‐based simulations of water balance. We examined the current and future distribution of Artemisia tridentata (big sagebrush) representing sagebrush ecosystems, which are widespread in semiarid western North America. For each approach, we calculated ensemble models from nine SDM methods and tested accuracy of each SDM with a null distribution. Climatic conditions included current conditions for 1970–1999 and two IPCC projections B1 and A2 for 2070–2099. Ecohydrological conditions were assessed by simulating soil water balance with SOILWAT, a daily time‐step, multiple layer, mechanistic, soil water model. Under current conditions, both climatic and ecohydrological SDM approaches produced comparable sagebrush distributions. Overall, sagebrush distribution is forecasted to decrease, with larger decreases under the A2 than under the B1 scenario and strong decreases in the southern part of the range. Increases were forecasted in the northern parts and at higher elevations. Both SDM approaches produced accurate predictions. However, the ecohydrological SDM approach was slightly less accurate than climatic SDMs (−1% in AUC, −4% in Kappa and TSS) and predicted a higher number of habitat patches than observed in the input data. Future predictions of ecohydrological SDMs included an increased number of habitat patches whereas climatic SDMs predicted a decrease. This difference is important for understanding landscape‐scale patterns of sagebrush ecosystems and management of sagebrush obligate species for future conditions. Several mechanisms can explain the diverging forecasts; however, we need better insights into the consequences of different datasets for SDMs and how these affect our understanding of future trajectories.
The Pseudoscience of Single-Sex Schooling
Authors: Halpern Diane F. , Eliot Lise , Bigler Rebecca S. , Fabes Richard A. , Hanish Laura D. , Hyde Janet , Liben Lynn S. , Martin Carol Lynn
Published: September 2011

Single-sex schooling lacks scientific support and may exaggerate sexism and gender stereotyping.
Electrically Controlled Nonlinear Generation of Light with Plasmonics
Authors: Cai Wenshan , Vasudev Alok P. , Brongersma Mark L.
Published: September 2011

A plasmonic structure is used to electrically produce frequency-doubled light.
Ironing Out Hydrogen Storage
Authors: Ott Sascha
Published: September 2011

The use of formic acid for storage of hydrogen fuel is enabled by an iron compound that catalyzes dehydrogenation
False Positive
Authors: Cohen Jon , Enserink Martin
Published: September 2011

A report in
Science
2 years ago that linked a mouse retrovirus, XMRV, to chronic fatigue syndrome astonished scientists and patients alike. But the theory soon began to take hits, and now, to all but a few researchers, it has completely unraveled.
Studies on Porcine Circovirus Type 2 Vaccination of 5-Day-Old Piglets
Authors: O'Neill K. C. , Shen H. G. , Lin K. , Hemann M. , Beach N. M. , Meng X. J. , Halbur P. G. , Opriessnig T.
Published: September 2011

Porcine circovirus type 2 (PCV2) vaccines have become widely used since they became available in 2006. It is not uncommon for producers to use PCV2 vaccines in pigs younger than what is approved by manufacturers. The objective of this study was to determine the efficacy of a chimeric and a subunit PCV2 vaccine administered at 5 or 21 days of age. Forty-eight PCV2-naïve piglets were randomly divided into six groups of eight pigs each. Vaccination was done at day 5 or day 21, followed by triple challenge with PCV2, porcine parvovirus (PPV), and porcine reproductive and respiratory syndrome virus (PRRSV) at day 49. Vaccinated pigs seroconverted to PCV2 approximately 14 days postvaccination and had a detectable neutralizing antibody response by 21 days postvaccination regardless of age at vaccination. At day 49, the pigs vaccinated with the chimeric vaccine had significantly higher levels of neutralizing antibodies than the pigs vaccinated with the subunit vaccine. After challenge, vaccinated pigs had significantly decreased levels of PCV2 viremia and a decreased prevalence and severity of microscopic lesions compared to the positive-control group, which had severe lymphoid lesions associated with abundant PCV2 antigen, compatible with PCV-associated disease. The results of this study indicate that, under the conditions of this study, vaccination of PCV2-naïve pigs at day 5 or day 21 resulted in development of a detectable humoral immune response and provided reduction or complete protection against PCV2 viremia and PCV2-associated lesions after triple challenge with PCV2, PPV, and PRRSV.
Comparison of a Newly Developed Automated and Quantitative Hepatitis C Virus (HCV) Core Antigen Test with the HCV RNA Assay for Clinical Usefulness in Confirming Anti-HCV Results
Authors: Kesli Recep , Polat Hakkı , Terzi Yuksel , Kurtoglu Muhammet Guzel , Uyar Yavuz
Published: September 2011

Hepatitis C virus (HCV) is a global health care problem. Diagnosis of HCV infection is mainly based on the detection of anti-HCV antibodies as a screening test with serum samples. Recombinant immunoblot assays are used as supplemental tests and for the final detection and quantification of HCV RNA in confirmatory tests. In this study, we aimed to compare the HCV core antigen test with the HCV RNA assay for confirming anti-HCV results to determine whether the HCV core antigen test may be used as an alternative confirmatory test to the HCV RNA test and to assess the diagnostic values of the total HCV core antigen test by determining the diagnostic specificity and sensitivity rates compared with the HCV RNA test. Sera from a total of 212 treatment-naive patients were analyzed for anti-HCV and HCV core antigen both with the Abbott Architect test and with the molecular HCV RNA assay consisting of a reverse transcription-PCR method as a confirmatory test. The diagnostic sensitivity, specificity, and positive and negative predictive values of the HCV core antigen assay compared to the HCV RNA test were 96.3%, 100%, 100%, and 89.7%, respectively. The levels of HCV core antigen showed a good correlation with those from the HCV RNA quantification (
r
= 0.907). In conclusion, the Architect HCV antigen assay is highly specific, sensitive, reliable, easy to perform, reproducible, cost-effective, and applicable as a screening, supplemental, and preconfirmatory test for anti-HCV assays used in laboratory procedures for the diagnosis of hepatitis C virus infection.
Cell-to-Cell Contact with Hepatitis C Virus-Infected Cells Reduces Functional Capacity of Natural Killer Cells
Authors: Yoon Joo Chun , Lim Jong-Baeck , Park Jeon Han , Lee Jae Myun
Published: September 2011

The distinct feature of hepatitis C virus (HCV) infection is a high incidence of chronicity. The reason for chronic HCV infection has been actively investigated, and impairment of innate and adaptive immune responses against HCV is proposed as a plausible cause. Whereas functional impairment of HCV-specific T cells is well characterized, the role and functional status of natural killer (NK) cells in each phase of HCV infection are still elusive. We therefore investigated whether direct interaction between NK cells and HCV-infected cells modulates NK cell function. HCV-permissive human hepatoma cell lines were infected with cell culture-generated HCV virions and cocultured with primary human NK cells. Cell-to-cell contact between NK cells and HCV-infected cells reduced NK cells' capacity to degranulate and lyse target cells, especially in the CD56
dim
NK cell subset, which is characterized by low-density surface expression of CD56. The decrease in degranulation capacity was correlated with downregulated expression of NK cell-activating receptors, such as NKG2D and NKp30, on NK cells. The ability of NK cells to produce and secrete gamma interferon (IFN-γ) also diminished after exposure to HCV-infected cells. The decline of IFN-γ production was consistent with the reduction of NK cell degranulation. In conclusion, cell-to-cell contact with HCV-infected cells negatively modulated functional capacity of NK cells, and the inhibition of NK cell function was associated with downregulation of NK-activating receptors on NK cell surfaces. These observations suggest that direct cell-to-cell interaction between NK cells and HCV-infected hepatocytes may impair NK cell function
in vivo
and thereby contribute to the establishment of chronic infection.
HIV-1 Infection Abrogates CD8+T Cell Mitogen-Activated Protein Kinase Signaling Responses
Authors: Crawford Timothy Q. , Ndhlovu Lishomwa C. , Tan Alice , Carvidi Alex , Hecht Frederick M. , Sinclair Elizabeth , Barbour Jason D.
Published: September 2011

Mitogen-activated protein kinase (MAPK) signaling pathways are dynamic and sensitive regulators of T cell function and differentiation. Altered MAPK signaling has been associated with the inflammatory and autoimmune diseases lupus and arthritis and with some pathogenic viral infections. HIV-1 infection is characterized by chronic immune inflammation, aberrantly heightened CD8+T cell activation levels, and altered T cell function. The relationship between MAPK pathway function, HIV-1-induced activation (CD38 and HLA-DR), and exhaustion (Tim-3) markers in circulating CD8+T cells remains unknown. Phosphorylation of the MAPK effector proteins ERK and p38 was examined by “phosflow” flow cytometry in 79 recently HIV-1-infected, antiretroviral-treatment-naïve adults and 21 risk-matched HIV-1-negative controls. We identified a subset of CD8+T cells refractory to phorbol 12-myristate 13-acetate plus ionomycin-induced ERK1/2 phosphorylation (referred to as p-ERK1/2-refractory cells) that was greatly expanded in HIV-1-infected adults. The CD8+p-ERK1/2-refractory cells were highly activated (CD38+HLA-DR+) but not exhausted (Tim-3 negative), tended to have low CD8 expression, and were enriched in intermediate and late transitional memory states of differentiation (CD45RA−CD28−CD27+/−). Targeting MAPK pathways to restore ERK1/2 signaling may normalize immune inflammation levels and restore CD8+T cell function during HIV-1 infection.
Immunopathogenic and Antibacterial Effects of H3N2 Influenza A Virus PB1-F2 Map to Amino Acid Residues 62, 75, 79, and 82
Authors: Alymova Irina V. , Green Amanda M. , van de Velde Nicholas , McAuley Julie L. , Boyd Kelli L. , Ghoneim Hazem E. , McCullers Jonathan A.
Published: September 2011

The influenza A virus protein PB1-F2 has been linked to the pathogenesis of both primary viral and secondary bacterial infections. H3N2 viruses have historically expressed full-length PB1-F2 proteins with either proinflammatory (e.g., from influenza A/Hong Kong/1/1968 virus) or noninflammatory (e.g., from influenza A/Wuhan/359/1995 virus) properties. Using synthetic peptides derived from the active C-terminal portion of the PB1-F2 protein from those two viruses, we mapped the proinflammatory domain to amino acid residues L62, R75, R79, and L82 and then determined the role of that domain in H3N2 influenza virus pathogenicity. PB1-F2-derived peptides containing that proinflammatory motif caused significant morbidity, mortality, and pulmonary inflammation in mice, manifesting as increased acute lung injury and the presence of proinflammatory cytokines and inflammatory cells in the lungs compared to peptides lacking this motif, and better supported bacterial infection with
Streptococcus pneumoniae
. Infections of mice with an otherwise isogenic virus engineered to contain this proinflammatory sequence in PB1-F2 demonstrated increased morbidity resulting from primary viral infections and enhanced development of secondary bacterial pneumonia. The presence of the PB1-F2 noninflammatory (P62, H75, Q79, and S82) sequence in the wild-type virus mediated an antibacterial effect. These data suggest that loss of the inflammatory PB1-F2 phenotype that supports bacterial superinfection during adaptation of H3N2 viruses to humans, coupled with acquisition of antibacterial activity, contributes to the relatively diminished frequency of severe infections seen with seasonal H3N2 influenza viruses in recent decades compared to their first 2 decades of circulation.
c-Cbl-Mediated Selective Virus-Receptor Translocations into Lipid Rafts Regulate Productive Kaposi's Sarcoma-Associated Herpesvirus Infection in Endothelial Cells
Authors: Chakraborty Sayan , ValiyaVeettil Mohanan , Sadagopan Sathish , Paudel Nitika , Chandran Bala
Published: September 2011

During target cell entry and infection, many enveloped and nonenveloped viruses utilize cell surface receptors that translocate into lipid rafts (LRs). However, the mechanism behind this translocation is not known. Kaposi's sarcoma-associated herpesvirus (KSHV) interacts with the human microvascular dermal endothelial (HMVEC-d) cell surface heparan sulfate (HS), integrins α3β1, αVβ3, and αVβ5, and the amino acid transporter x-CT protein and enters via c-Cbl-bleb-mediated macropinocytosis (Veettil et al., J. Virol.
82:
12126-12144, 2008; Veettil et al., PLoS Pathog.
6:
e1001238, 2010). Here we have demonstrated that very early during infection (1 min postinfection), c-Cbl induced the selective translocation of KSHV into the LR along with the α3β1, αVβ3, and x-CT receptors but not αVβ5. Activated c-Cbl localized with LRs at the junctional base of macropinocytic blebs. LR-translocated α3β1 and αVβ3 were monoubiquitinated, leading to productive macropinocytic entry, whereas non-LR-associated αVβ5 was polyubiquitinated, leading to clathrin entry that was targeted to lysosomes. c-Cbl knockdown blocked the macropinocytosis and receptor translocation and diverted KSHV to a clathrin-lysosomal noninfectious pathway. Similar results were also seen by LR disruption with MβCD. These studies provide the first evidence that c-Cbl regulates selective KSHV-α3β1, -αVβ3, and -x-CT receptor translocations into the LRs and differential ubiquitination of receptors which are critical determinants of the macropinocytic entry route and productive infection of KSHV. Our studies suggest that interventions targeting c-Cbl and LRs are potential avenues to block KSHV infection of endothelial cells.
ŁOJASIEWICZ INEQUALITY FOR POLYNOMIAL FUNCTIONS ON NON-COMPACT DOMAINS
Authors: TIEP DINH SI , VUI HA HUY , THAO NGUYEN THI
Published: September 2011

In this paper we give some versions of the Łojasiewicz inequality on non-compact domains for polynomial functions. We also point out some relations between the existence Łojasiewicz inequality and the phenomenon of singularities at infinity.
Study on Interface Adhesion between Phase Change Material Film and SiO2 Layer by Nanoscratch Test
Authors: Zhou Xilin , Wu Liangcai , Song Zhitang , Rao Feng , Ren Kun , Peng Cheng , Guo Xiaohui , Liu Bo , Feng Songlin
Published: September 2011

Temperature dependent interfacial adhesion strength between phase change material film and a SiO2 layer was investigated employing Nano Indenter®. Phase change materials of Ge2Sb2Te5 and Si2Sb2Te6 were adopted for a comparative study. The decrease of adhesive strength with an increased annealing temperature can be deduced from the optical micrographs of the two cases. Critical load obtained from the nanoscratch tests was introduced to quantitative characterize the interfacial adhesion strength of the samples. Scanning electron microscope and energy dispersive spectrometer were utilized to further analysis the adhesive properties of the interfaces. Results show that Si2Sb2Te6 has better adhesive performance than Ge2Sb2Te5 with SiO2 due to its higher activation energy and weaker thickness variation upon crystallization as well as its smaller crystal grain size in the crystalline state. Considering the adhesive strength with SiO2, Si2Sb2Te6 is a preferable candidate over Ge2Sb2Te5 for future high density phase change random access memory application.
Excited States of 3d3 Electrons in K2SiF6:Mn4+ Red Phosphor Studied by Photoluminescence Excitation Spectroscopy
Authors: Arai Takahiro , Adachi Sadao
Published: September 2011

This paper reports on a study of the photoluminescence excitation (PLE) spectra of Mn4+-activated K2SiF6 phosphor at 20 and 300 K. Measurements of the PLE spectra show that the sharp red emissions (2Eg →4A2g) at ∼630 nm are most efficiently excited by irradiation into the spin-allowed transitions 4A2g →4T2g (∼460 nm) and 4A2g →4T1g (∼360 nm). The first efficient excitation band 4A2g →4T2g is structureless at 300 K but shows a sharp origin and some oscillatory peaks at 20 K. A Fourier transform technique is used for analyzing such oscillatory peaks. The second excitation band 4A2g →4T1g shows a structureless shape even at a low temperature (20 K). The third excitation band with a peak at ∼250 nm is very weak and could be assigned as the 4A2g →4T1g transition. The direct excitation of the 2Eg state is also found to produce the sharp red emissions at ∼630 nm with a negligibly small offset in the configurational coordination. The Franck–Condon analysis makes it possible to accurately determine the zero-phonon line energies in the 3d3 electron transitions of the MnF6
2- octahedron.
Effect of Zr Addition on the Magnetization Reversal Behavior for α-Fe/Pr2Fe14B Nanocomposite Alloys
Authors: Pan Minxiang , Zhang Pengyue , Ge Hongliang , Hong Zhanglian , Wu Qiong , Jiao Zhiwei , Yang Hangfu
Published: September 2011

The microstructure and magnetic properties of the Zr-doped α-Fe/Pr2Fe14B nanocomposite magnets prepared by melt-spinning method have been studied by X-ray diffraction (XRD), vibrating sample magnetometer (VSM) and superconducting quantum interference device (SQUID) measurements. The magnetization reversal behavior during the recoil processes of nanocomposite alloys has been investigated by analyzing the hysteresis curves and recoil loops of demagnetization curves. An enhanced magnetic properties has been obtained by the addition of 1 at. % Zr in α-Fe/Pr2Fe14B alloys, where the coercivity H
c increases from 470.7 to 793.2 kA/m, the maximum energy product (B
H)max from 66.8 to 90.8 kJ/m3, the remanence ratio M
r/M
s from 0.74 to 0.77. The recoil loop results show that the maximum value of the integrated recoil loop area for 1 at. % Zr doped sample is quietly low of 1.87×10-3, only 1/2 for the Zr-free and 1/3 for 5 at. % Zr doped samples respectively. This result indicates that the 1 at. % Zr doped sample has a lower energy loss, resulting from a low recoverable portion of the magnetization remaining as long as the applied reversal field is below the coercivity H
c. This study provides a promising guideline for the future fabrication of low-energy-loss nanocomposite magnets for electric machines and generators.
In situ Monitoring of Target Voltage in Magnetron Reactive Sputtering of ZnO
Authors: Kim Youngseok , Jang Samseok , Park Bum-ryull , Byun Dongjin
Published: September 2011

Zinc oxide (ZnO) films were deposited on glass substrates by radio-frequency (RF) magnetron reactive sputtering at room temperature. With the relationship between deposition rate and oxygen flow, the appropriate deposition condition was not set up easily for reactive sputtering. The mechanisms between the sputtered material and the reactive gas may cause some processing stability problems. Therefore, it is required to find the in situ way of determining which mode films would be deposited before deposition. The in situ monitoring of the target voltage during deposition can be helpful for obtaining transparent and conductive films. With the in situ monitoring of the target voltage, the properties of ZnO thin films can be predicted and selected within metallic, transition, and oxide modes.
Growth of High-Quality Si-Doped AlGaN by Low-Pressure Metalorganic Vapor Phase Epitaxy
Authors: Shimahara Yuki , Miyake Hideto , Hiramatsu Kazumasa , Fukuyo Fumitsugu , Okada Tomoyuki , Takaoka Hidetsugu , Yoshida Harumasa
Published: September 2011

In this paper we report the growth of Si-doped AlGaN on an AlN/sapphire substrate by low-pressure metalorganic vapor phase epitaxy (LP-MOVPE) with an in situ monitoring system to fabricate a high-quality film with controlled thickness. The AlN mole fraction in AlGaN can be controlled by adjusting the growth temperature. We also discuss the quality and growth mechanism of AlGaN on AlN. GaN and AlGaN with an AlN mole fraction of 0.28 were free from stress because of the occurrence of three-dimensional (3D) growth. The lattice constant a of AlGaN with an AlN mole fraction of 0.40 was larger than that at an AlN mole fraction of 0.28 despite the two-dimensional (2D) growth mode. This indicates that the lattice mismatch between AlGaN and the underlying AlN adversely affects the crystal quality. AlGaN with an AlN mole fraction of over 0.60 was coherently grown on AlN owing to the fact that the AlN/sapphire template used in this work was subjected to compression. For this reason, in the samples with an AlN mole fraction of over 0.6, the crystal quality was high because of the coherent growth on the underlying AlN. Moreover, Si doping was performed for AlGaN. The carrier concentration increased linearly up to a Si concentration of 2 ×1018 cm-3, indicating that the activation rate was approximately 1.
Theoretical Study on Epitaxial Graphene Growth by Si Sublimation from SiC(0001) Surface
Authors: Kageshima Hiroyuki , Hibino Hiroki , Yamaguchi Hiroshi , Nagase Masao
Published: September 2011

The growth of epitaxial graphene on the SiC(0001) surface is theoretically studied by assuming silicon (Si) sublimation from the surface. Our results indicate that a new graphene sheet grows from the interface between the old graphene sheets and SiC substrate, as found in our previous study on graphene growth by carbon (C) deposition. Graphene growth requires overcoming rather lower energy barriers until 0-monolayer graphene (buffer layer) is formed. Further growth toward formation of 1-monolayer graphene requires overcoming energy barriers higher by about 0.7 eV, which indicates that the growth preferably stops once when 0-monolayer graphene is formed. Compared with the C deposition case, the growth requires overcoming the energy barrier higher by about 0.7 eV, which indicates that the graphene growth is more difficult. In addition, the nonuniform growth of surface C aggregates is thought to degrade the quality of the grown graphene. The C-rich condition is therefore important for obtaining high-quality graphene. The experimental graphene growth is considered to proceed similarly to the C deposition case rather than the Si sublimation case.
Excitation Temperature Measurement in Liquid Electrode Plasma
Authors: Kumai Miyuki , Takamura Yuzuru
Published: September 2011

Liquid electrode plasma atomic emission spectrometry (LEP-AES) is a novel elemental analysis method where a sample solution is placed in a small cuvette that has a narrow microchannel at the center. High voltage is applied to the solution from both ends of the cuvette channel, and then microplasma is generated in the channel. The microplasma is employed in atomic emission spectrometry as a plasma source. Excitation temperature was deduced using a Boltzmann plot. The temperature was determined to be 6200 K with a plastic chip at an applied voltage of 800 V. To investigate effects of the experimental conditions on excitation temperature, applied voltage, type of acid, and the shape of the cross section of a microchannel at the center of the cuvette were varied. The excitation temperature was not influenced by applied voltage or type of acid, but was affected by the shape of the cross section of the microchannel.
Effect of Moisture on the Frequency-Dependent Current of an AlGaN/GaN High-Electron-Mobility Transistor
Authors: Kim Jeong Jin , Yang Gye Mo , Shim Kyu-Hwan , Yang Jeon Wook
Published: September 2011

The effect of moisture on the current of an AlGaN/GaN high-electron-mobility transistor was investigated. When the gate voltage was swept from -5 to 0 V at a drain voltage of 7 V, the current decreased with the sweep frequency from 38 mA at 0.1 Hz to 15 mA at 100 kHz. However, the decrease was mitigated to 29 mA by moisturizing the ambient, and a marked current decrease in a pulsed operation was alleviated by moisture from 7.4 to 33 mA at 100 kHz with a 10% duty cycle. The binding of polarized H2O to negatively charged traps was proposed as the reason for the alleviation of the current degradation.
Langasite Crystal Microbalance for Development of Reactive Surface Preparation of Silicon Carbide Film Deposition from Monomethylsilane Gas
Authors: Habuka Hitoshi , Kote Ken-Ichi
Published: September 2011

A silicon carbide chemical vapor deposition (CVD) process at room temperature was developed using monomethylsilane (MMS) gas by an in situ measurement method using a langasite crystal microbalance (LCM). The phenomenon occurring on the LCM was evaluated by monitoring the frequency change during the processes and by comparing the frequencies in a steady state in ambient hydrogen without the use of any additional gases. The entire process was performed on the LCM, which could be used to evaluate the reactive surface preparation and the silicon carbide film deposition. To produce a reactive surface, a silicon-rich thin film was prepared by the CVD technique using MMS gas at 800 °C. Because the LCM frequency continuously decreased along with the MMS gas supply at room temperature, the silicon carbide film deposition was found to be continuous for 1 min.
Evaluation of Acoustic Anisotropy to Image Defects in Weld Metal by Ultrasonic Phased Array
Authors: Shintaku Yohei , Ohara Yoshikazu , Yamanaka Kazushi
Published: September 2011

An ultrasonic phased array (PA) does not work well in some weld metals owing to the strong acoustic anisotropy. However, the analysis of anisotropy for the compensation of the shift of the defect image in the PA has not been performed. In this study, we compared the results of imaging a slit in a Ni-based weld metal, commercially available as Inconel alloy 600, in an experiment and in simulations using the analytical solution of group velocity or the finite-difference time-domain (FDTD) method. As a result, we succeeded in reproducing the shift and broadening of the defect image obtained in an experiment by the simulations.
Optical Design and Analysis of a Laser Expander for a Blu-ray Pickup Head for Synchronous Detection of the Tilt Angle and Displacement on the Test Plane
Authors: Sun Wen-Shing , Lin Yan-Nan , Chang Jenq-Yang
Published: September 2011

An optical design is developed for a Blu-ray pickup head with a laser expander that can synchronously detect the linear displacement and two-dimensional angular tilts at the test plane. To improve the signal accuracy of the photo detector, a laser expander is used to transform the shape of the laser beam from elliptical to circular. A quadrant detector as used to detect the relative relationship between the V
A, V
B, V
C, V
D signals, can be used to measure the tilt angle and displacement at the test plane. Measurement detection and analysis is based on one normalized focus error signal (NFES) and two angular signals. The optical efficiency of the Blu-ray pickup head with laser expander is 59.29%. The optical efficiency of the currently used commercial pickup head is only 8.08%. Tolerance analysis is also considered in the performance requirements.
Expectation-Maximization Based Adaptive Threshold Detection Algorithm for Multi-Level Holographic Data Storage
Authors: Kim Jinyoung , Lee Jaejin , Park Taehyung , Im Sungbin
Published: September 2011

We propose an adaptive threshold detector algorithm for multi-level holographic data storage based on the expectation-maximization (EM) method. In this paper, the signal intensities that are passed through the four-level holographic channel are modeled as a four Gaussian mixture with unknown DC offsets and the threshold levels are estimated based on the maximum likelihood criterion. We compare the bit error rate (BER) performance of the proposed algorithm with the non-adaptive threshold detection algorithm for various levels of DC offset and misalignments. Our proposed algorithm shows consistently acceptable performance when the DC offset variance is fixed or the misalignments are lower than 20%. When the DC offset varies with each page, the BER of the proposed method is acceptable when the misalignments are lower than 10% and DC offset variance is 0.001.
k/(k+1) Tone-Controllable Codes for Holographic Data Storage
Authors: Park Donghyuk , Lee Jaejin
Published: September 2011

In this paper, we propose k/(k+1) tone-controllable (TC) codes for holographic data storage system which can control the rate of ON and OFF pixels within each data page. We introduce a method for making an encoding table for the proposed k/(k+1) TC code and we analyze the features of the proposed code. In addition, we analyze the k/(k+n) TC code where n is 1–5.
Tunable Surface Plasmon Resonances Based on Chromium Disk Array Containing Liquid Crystals
Authors: Shyu Jia-Hong , Lin Yu-Chun , Lee Huang-Ming , Hsieh Chia-Ting , Huang Chi-Yen , Wu Jong-Ching
Published: September 2011

The tunable surface plasmon resonances of an indium tin oxide (ITO) cell embedded with a chromium disk array and liquid crystals (LCs) have been investigated. The chromium disk array with a diameter of 300 nm and a period of 600 nm was fabricated on one ITO film and the LCs were infiltrated into the ITO cell. The effective refractive indices of the sandwiched LCs may be tuned from 1.51 to 1.73 by applying external electrical fields across the two ITO films. The optical transmission spectra reveal two resonances that may be modulated from 482 to 575 nm and from 670 to 723 nm within the range of tuning. In addition, the tunable surface plasmon resonances illustrate hysteresis behaviors. These results are identified to be associated with the alignment of LCs that is modulated by the electrical fields.
Broad Detecting Range of Objective-Based Surface Plasmon Resonance Sensor via Multilayer Structure
Authors: Lan Tzu-Hsiang , Chung Yi-Kuan , Tien Chung-Hao
Published: September 2011

The demand of pursuing higher resolution drives the instrumental development of a surface plasmon resonance (SPR) sensor to shift from Kretchmann to objective-based configuration. However, its maximum sensing refractive index is restricted by the numerical aperture of an objective lens. Based on the mode conversion, we proposed a multilayer structure to extend the detecting range up to 11% (from 1.28 to 1.42) for a 1.45 objective lens via a transformed SPR mode. This technique not only overcomes intrinsic constraint but also reduces the cost.
Investigation on Thickness Effect of Ultrathin Vinylidene Fluoride/Trifluoroethylene Copolymer Films
Authors: Mabuchi Yuichiro , Nakajima Takashi , Chaudhuri Kaustav , Evans James E. , Browning Nigel D. , Okamura Soichiro
Published: September 2011

We investigated the thickness effect on ferroelectric properties of vinylidene fluoride (VDF)/trifluoroethylene (TrFE) copolymer films in the region of 9.7–230 nm. Film thickness was estimated from cross-sectional transmission electron microscope (TEM) images. Relative permittivity calculated using precise thickness measurements decreased from 10 to 5.3 with decreasing thickness. Remnant polarization gradually decreased from 80 to 34 mC/m2 with decreasing thickness, whereas maximum polarization was almost constant. These results suggested the existence of a dead layer with a low permittivity at the interface between the VDF/TrFE copolymer films and electrodes. Finally, the thickness of the dead layer was estimated to be 4.1 nm by assuming the existence of two layers with different permittivities.
Effect of Dopant on Piezoelectric Properties of Lead-Free BiFeO3–BaTiO3Film
Authors: Sasaki Tsutomu , Hirabayashi Yasutoshi , Kobayashi Hiroyuki , Sakashita Yukio
Published: September 2011

To realize high-performance lead-free piezoelectric materials, we have selected BiFeO3as the rhomboheral phase material and BaTiO3as the tetragonal phase material, following the MPB mechanism of PZT. To further improve the piezoelectric properties of BiFeO3–BaTiO3(BFBT) thin films, we investigated the effect of dopant on the piezoelectric properties of BFBT. Considering both Shanon effective ionic radii and valence number, we have selected Sr2+(BFBT–SrTiO3, abbreviated as BFBT-ST) and Nb5+(abbreviated as BFBT-Nb) substitutions. BFBT-ST and BFBT-Nb films were epitaxially grown by pulsed laser deposition on an epitaxial SrRuO3/MgO/Si(100) substrate. The piezoelectric constantd33AFMis estimated from the slope of the maximum displacement and the maximum voltage strength by atomic force microscopy. Compared with 0.8BF0.2BT films withd33AFM= 65 pm/V, the 0.8BF0.2BT–Nb2.5% films achievedd33AFM= 78 pm/V. The displacement curve of 0.8BF0.2BT–Nb2.5% became soft with the occurrence of a hysteresis shape, compared with that of 0.8BF0.2BT. Moreover, thed33AFMof 0.77BF0.13BT–0.1ST (BF/BT ratio= 0.85/0.15) was 83 pm/V, compared with thed33AFM(58 pm/V) of 0.85BF0.15BT. According to these results, we confirmed that the Sr2+and Nb5+substitutions improve the piezoelectric properties of BFBT.
Influence of SrRuO3 Bottom Electrode Thickness on Electric Properties of (Bi,Pr)(Fe,Mn)O3 Ultra-Thin Film Capacitor
Authors: Kawae Takeshi , Tsukada Yoshinori , Nakajima Takashi , Terauchi Yuki , Nomura Yukihiro , Okamura Soichiro , Morimoto Akiharu
Published: September 2011

(Pr,Mn)-codoped BiFeO3 (BPFM) ultra-thin films of 85 nm thickness were deposited on a SrRuO3 (SRO)-coated (100) Nb-doped SrTiO3 substrate by pulsed laser deposition. Regardless of the SRO film thickness, the SRO and BPFM thin films showed perfectly (h00)-orientation on the substrate. On the other hand, the surface morphology and leakage current of the BPFM films strongly depended on the SRO film thickness. The BPFM ultra-thin film on a 115 nm thick SRO electrode shows a hysteresis loop without any influences of leakage current. The remnant polarization 2P
r and the coercive voltage 2V
c at the maximum applied voltage of 10 V are 82 µC/cm2 and 7.2 V, respectively.
Effects of Electrodes on Dielectric and Piezoelectric Properties of Lead Magnesium Niobate–Lead Titanate Single-Crystal Transducer
Authors: Yamamoto Noriko , Itsumi Kazuhiro , Hosono Yasuharu , Yamashita Yohachi
Published: September 2011

The effects of four types of electrodes, sputtered gold (Au), titanium/Au (Ti/Au), chromium/Au (Cr/Au), and fired silver (Ag), on the dielectric and piezoelectric properties of a lead magnesium niobate–lead titanate (PMN–PT) single-crystal transducer near the morphotropic phase boundary composition were investigated to obtain better properties of the transducer for application in medical ultrasound probes. The Au electrode sample showed the highest piezoelectric constant d
33 = 1710 pC/N and the Cr/Au electrode sample showed the highest coercive field E
c = 3.1 kV/cm. Those differences were derived from several factors, namely, the dielectric constant at phase change temperature, the crystallinity on the surface caused by electrode forming treatment, adhesion strength, and the thickness of the electrodes. Changing the electrode is an easier way to realize the desired piezoelectric properties than crystal composition control. Thus, this information can prove useful for the application of the PMN–PT transducer in medical ultrasound probes.
Shrinkage Behaviors and Sintering Mechanism of BaTiO3 Ceramics in Two-Step Sintering
Authors: Hoshina Takuya , Kigoshi Yoichi , Furuta Tsutomu , Takeda Hiroaki , Tsurumi Takaaki
Published: September 2011

The shrinkage behaviors of BaTiO3 ceramics in a nonisothermal process were quantitatively monitored to clarify the mechanism of two-step sintering. During the increase in temperature, shrinkage behaviors due to grain boundary diffusion, volume diffusion, and grain rearrangement were observed. From the analysis of the shrinkage curve and the observation of the microstructure, the first step in two-step sintering was interpreted as a process for eliminating large pores by grain rearrangement. In contrast, the second step was interpreted as a process for final densification by volume diffusion. It was clarified that the analysis of shrinkage behaviors was useful for understanding two-step sintering and for determining suitable sintering conditions.
Synthesis and Dielectric Properties of Mn-Doped BaTi2O5 Ceramics
Authors: Akishige Yukikuni , Honda Kazuo , Tsukada Shinya
Published: September 2011

High-density ceramics of BaTi2O5 have been fabricated by a conventional sintering method using both sol–gel-derived BaTi2O5 powders and MnO2 additives of 0.2–0.8 wt %. The effects of sintering conditions on the densification, microstructural evolution and dielectric properties are investigated. As the effect of Mn addition, the BaTi2O5 phase becomes stable at least up to 1250 °C, and a significant densification is achieved at temperatures as low as 1200–1250 °C. The dielectric constant ε' vs temperature T curve of the MnO2-added ceramics exhibits a broad maximum ε'max at the ferroelectric phase transition temperature T
C, which is 140 °C lower than that of the nondoped ceramics. Among the ceramics with different Mn contents, the 0.2 wt % MnO2-added ceramics have the largest ε'max of 470 at 328 °C and the smallest tan
δ of <0.05 at a high temperature of around 520 °C at 1 MHz. We observed a ferroelectric D–E hysteresis loop for the first time in the polycrystalline form of BaTi2O5.
Effects of Lattice Constant and Sintering Atmosphere on Substitution of Sn2+ Ions at Ba Site in (Ba,Ca)TiO3 Perovskites: Experimental and Theoretical Studies
Authors: Suzuki Shoichiro , Honda Atsushi , Higai Shin'ichi , Ando Akira , Wada Nobuyuki , Takagi Hiroshi
Published: September 2011

The Sn2+ substitution into the Ba site in BaTiO3-based perovskites was experimentally and theoretically investigated. We clarified two factors promoting the Sn2+ substitution: the sintering partial pressure of oxygen (pO2) and the lattice size of BaTiO3. We found the optimum region of sintering pO2, where a high tetragonality and a high temperature of transition from the ferroelectric phase to the paraelectric phase are realized. It was also found that decreasing lattice size by Ca doping is effective for substituting Sn2+ into the Ba site in BaTiO3. These results provide insights for exploring new ceramics containing Sn2+ that possess better ferroelectric properties.
Analysis of Mechanism of Improvement in Highly Accelerated Lifetime via Measurement of Vanadium Valence in Multilayer Ceramic Capacitors
Authors: Shibahara Takeshi , Yonezawa Yu , Satoh Jun , Kido Osamu , Natsui Hidesada
Published: September 2011

The valence of vanadium was measured by electron paramagnetic resonance in order to explain the decrease in insulation resistance (IR) and the improvement in highly accelerated lifetime that resulted from the addition of vanadium. V4+ was detected in specimens with vanadium contents of 0.20 and 0.30 mol %, while no V4+ was detected in a specimen with a vanadium content of 0.06 mol %. It was also revealed that the content of the vanadium except for V4+ are the main factor responsible for the decrease in IR and the improvement in lifetime. The impedance of BaTiO3-based materials in multilayer ceramic capacitors with various vanadium contents was investigated in order to determine the mechanism of improving the highly accelerated lifetime using a four resistance and capacitor section electrical equivalent circuit. All four resistance components (R components) decreased with an increase in vanadium content. During the lifetime test, all four R components were degraded. In particular, the R component corresponding to the ceramic/internal electrode interface regions was more strongly degraded than the other three R components, and it was found that this component was the main factor responsible for the degradation of IR during the test. The resistance degradation of this component tended to occur slowly when the vanadium content increased, which resulted in the improvement in lifetime. The primary part of this degradation was implied to be controlled by diffusion.