bluuebunny/crossref_metadata_2025 huggingface dataset:
Acoustic Rayleigh scattering at individual micron-sized bubbles
Authors: Sboros V. , Pye S. D. , Anderson T. A. , Moran C. M. , McDicken W. N.
Published: March 2007

A microacoustic system based on a wide-bandwidth commercial piezoelectric transducer is presented in this letter. The system allows objective measurement of nonlinear Rayleigh scatter from single microbubbles. Two different types of microbubbles were exposed to a range of ultrasonic frequencies and amplitudes. Statistical examination of their scatter provides an understanding of their dissolution/destruction behavior and an insight on inertial cavitation. These high sensitivity measurements are key to the understanding of nonlinear scatter, may be employed to devise new signal processing techniques for imaging and better microbubble engineering.
Subnitride and valence band offset at Si3N4∕Si interface formed using nitrogen-hydrogen radicals
Authors: Higuchi Masaaki , Sugawa Shigetoshi , Ikenaga Eiji , Ushio Jiro , Nohira Hiroshi , Maruizumi Takuya , Teramoto Akinobu , Ohmi Tadahiro , Hattori Takeo
Published: March 2007

The authors measured soft x-ray-excited angle-resolved photoemission from Si 2p, N 1s, and O 1s core levels, and valence band for nitride films formed on Si(100), Si(111), and Si(110) using nitrogen-hydrogen radicals with the same probing depth. The Si3N4∕Si interfaces formed exhibited an almost abrupt compositional transition. Furthermore, the crystal orientation of Si substrate affects the total areal density of subnitrides but not the valence band offset at the Si3N4∕Si interface.
Nanoscale polarization manipulation and imaging of ferroelectric Langmuir-Blodgett polymer films
Authors: Rodriguez Brian J. , Jesse Stephen , Kalinin Sergei V. , Kim Jihee , Ducharme Stephen , Fridkin V. M.
Published: March 2007

Piezoresponse force microscopy has been used to manipulate and image polarization of ferroelectric polymer Langmuir-Blodgett films at the nanoscale, achieving polarization control with a resolution below 50nm and imaging resolution below 5nm. Individual regions showed square polarization-voltage hysteresis loops, demonstrating bistability of the polarization state. Arbitrary polarization patterns could be repeatedly written and erased with a resolution of 25to50nm, limited by grain size, demonstrating the potential for high-density data storage and retrieval at densities exceeding 250Gbits∕in2.
Creep in protective α-Al2O3 thermally grown on β-NiAl
Authors: Veal B. W. , Paulikas A. P. , Hou P. Y.
Published: March 2007

The authors report systematic measurements of creep relaxation in α-Al2O3, thermally grown in air on (100) single crystals of stoichiometric β-NiAl, at temperatures between 950 and 1100°C. Creep was monitored using time dependent in situ measurements of strain relaxation in the oxide following imposition of a stress resulting from a sudden temperature change. The in-plane elastic strain was obtained using a sin2ψ x-ray diffraction technique exploiting synchrotron radiation. The authors found that strain relaxation rates were comparable to those observed in fine grained α-Al2O3 ceramics when the latter results were extrapolated to the lower temperatures examined here. Creep rates at stress levels of 100MPa, or less, are proportional to σn, with n⩽2, consistent with a diffusional creep mechanism.
Identification of modes and single mode operation of sapphire-bonded photonic crystal lasers under continuous-wave room temperature operation
Authors: Shih M. H. , Bagheri Mahmood , Mock Adam , Choi S. J. , O’Brien J. D. , Dapkus P. D. , Kuang Wan
Published: March 2007

Sapphire-bonded photonic crystal laser cavities were fabricated and characterized under room temperature continuous-wave operation, and the single mode lasing with a side-mode-suppression ratio of 28dB was observed. The lasing modes of the photonic crystal cavities were characterized and compared to calculated spectra from the three-dimensional finite-difference time-domain method.
Self-assembled periodic nanoporous network in multifunctional ZrO2–CeO2–(La0.8Sr0.2)MnO3 composites
Authors: Sharma Vaneet , Jiang Jiechao , Hossu Maria , Koymen Ali R. , Priya Shashank
Published: March 2007

This letter reports the structural characteristics of the self-assembled surface nanostructure in the 0.75wt% (Zr0.88Ce0.12)O2–0.25wt% (La0.8Sr0.2)MnO3 ceramics. The surface consists of periodic porous network with islandlike structures occurring at the triple boundary junctions. The pores were found to have the diameter in the range of 150–200nm with the thickness of the porous surface layer of the order of 100nm. The pore distribution was quasiperiodic with the spacing in the range of 50–150nm. The formation of the nanoporous network is correlated to the structural transformation occurring in ZrO2 system.
Correlation between electron and negative O− ion emission during reactive sputtering of oxides
Authors: Mahieu S. , Depla D.
Published: March 2007

The energy distribution of negative O− ions has been measured during the reactive magnetron sputtering of 13 different target materials by the means of energy resolved mass spectrometry. For the same series of target materials the ion-induced secondary electron emission coefficient was determined in an earlier published research. A correlation between this ion-induced secondary electron emission coefficient and the emission of the high energetic negative O− ions was observed. This correlation should be taken into consideration in the selection of oxides for their high electron emission coefficients as these materials will emit at the same time negative O− ions.
Mechanism of molecular beam epitaxy growth of GaN nanowires on Si(111)
Authors: Debnath R. K. , Meijers R. , Richter T. , Stoica T. , Calarco R. , Lüth H.
Published: March 2007

GaN nanowires have been grown without external catalyst on Si(111) substrates by plasma-assisted molecular beam epitaxy. Nanowire aspect ratios (length/diameter) of about 250 have been achieved. During the initial stage of the growth, there is a nucleation process in which the number of wires increases and the most probable nucleation diameter of about 10nm has been observed, which slowly increases with deposition time. For deposition time longer than the nucleation stage, the nanowire length as a function of diameter monotonically decreases. This phenomenon can be explained by adatom diffusion on the nanowire lateral surface towards the tip.
Defect-mediated surface morphology of nonpolar m-plane GaN
Authors: Hirai A. , Haskell B. A. , McLaurin M. B. , Wu F. , Schmidt M. C. , Kim K. C. , Baker T. J. , DenBaars S. P. , Nakamura S. , Speck J. S.
Published: March 2007

The role of extended defects in determining the atomic scale surface morphology of nonpolar {11¯00} m-plane gallium nitride has been elucidated. The heteroepitaxially grown m-GaN films are commonly reported to yield striated surface morphologies (slate morphology) correlated with their high densities of basal plane stacking faults. Here, the growth window was explored to allow nonslate morphologies for hydride vapor phase epitaxy. Lateral epitaxial overgrowth was then utilized to produce m-GaN films with three regimes of different extended defect contents. Elimination of stacking faults from the m-GaN yielded step-flow features with an average step height of 4–7 ML even for slate morphology growth conditions.
Role of gross well-width fluctuations in bright, green-emitting single InGaN∕GaN quantum well structures
Authors: van der Laak Nicole K. , Oliver Rachel A. , Kappers Menno J. , Humphreys Colin J.
Published: March 2007

Gross well-width fluctuations have been observed by transmission electron microscopy (TEM) in single InGaN∕GaN quantum wells (QWs) grown by metal-organic vapor phase epitaxy. Similar thickness variations are observed in commercial, green InGaN∕GaN multi-QW light emitting diodes. Atomic force microscopy studies of equivalent epilayers suggest that these fluctuations arise from a network of interlinking InGaN strips, which are found (using TEM) to be indium rich at their centers. Plan-view TEM indicates that 90±8% of all threading dislocations (TDs) intersect the QW plane between the InGaN strips. Excitons may be localized at the strips’ centers, preventing nonradiative recombination at TDs.
Ion collection by planar Langmuir probes: Sheridan’s model and its verification
Authors: Lee Dongsoo , Hershkowitz Noah
Published: March 2007

Data analysis from planar Langmuir probes normally assumes that the sheath effects are not significant in determining electron density and temperature when the Debye length is small compared to the probe radius. However, analysis of ion saturation current requires careful attention due to sheath expansion near the probe electrode. It is experimentally verified for the first time that Sheridan’s numerical model [T. E. Sheridan, Phys. Plasmas 7, 3084 (2000)] provides a correct method to measure the ion saturation current for which the ion density agrees with the electron density in argon plasmas.
Precision analog integrator with voltage hold
Authors: Holt S. , Skyba P.
Published: March 2007

In some applications, like a magnetization and demagnetization of ordinary and superconducting magnets driven by the voltage controlled current sources, it is desirable to change the voltage smoothly and linearly toward an adjusted value and then hold this value in time. A circuit is presented that allows: (i) the slow, smooth, and linear change of the integrator output voltage without steps and (ii) the ability to hold the output voltage at a value given by a reference source. In a hold regime, the output voltage is stabilized by a negative feedback. A stability of one part of 105 at the output voltage of 2 V was achieved over a 12 h period.
Lateral epitaxial overgrowth of aluminum nitride on patterned silicon carbide substrates by hydride vapor phase epitaxy
Authors: Kamber Derrick S. , Wu Yuan , Letts Edward , DenBaars Steven P. , Speck James S. , Nakamura Shuji , Newman Scott A.
Published: March 2007

This letter reports on the reduction of threading dislocation densities in AlN films via lateral epitaxial overgrowth by hydride vapor phase epitaxy. A variety of different stripe patterns were used to produce fully coalesced AlN films. Transmission electron microscopy (TEM) was used to assess the structural quality of these films. TEM determined that the dislocation density in the laterally grown wing regions was less than 8.3×106cm−2 as compared to 1.8×109cm−2 in the seed regions. Atomic force microscopy revealed that the films have a smooth surface morphology with a rms roughness of 0.71nm over 10×10μm2 sampling areas.
Coherent detection of terahertz pulses based on two-photon absorption in a photodiode
Authors: Schneider Arno , Günter Peter
Published: March 2007

The authors present a simple and robust method for the measurement of the terahertz-induced lensing effect that may be used for the coherent detection of few-cycle terahertz pulses. It is based on two-photon absorption of a 1.5μm probe pulse in a standard silicon photodiode. The change in the spatial probe pulse profile caused by terahertz-induced lensing leads to a variation of the diode signal that is induced by two-photon absorption even though the total pulse energy has remained constant. This variation is shown to be proportional to the terahertz electric field.
Extreme hydrogen plasma densities achieved in a linear plasma generator
Authors: van Rooij G. J. , Veremiyenko V. P. , Goedheer W. J. , de Groot B. , Kleyn A. W. , Smeets P. H. M. , Versloot T. W. , Whyte D. G. , Engeln R. , Schram D. C. , Cardozo N. J. Lopes
Published: March 2007

A magnetized hydrogen plasma beam was generated with a cascaded arc, expanding in a vacuum vessel at an axial magnetic field of up to 1.6T. Its characteristics were measured at a distance of 4cm from the nozzle: up to a 2cm beam diameter, 7.5×1020m−3 electron density, ∼2eV electron and ion temperatures, and 3.5km∕s axial plasma velocity. This gives a 2.6×1024H+m−2s−1 peak ion flux density, which is unprecedented in linear plasma generators. The high efficiency of the source is obtained by the combined action of the magnetic field and an optimized nozzle geometry. This is interpreted as a cross-field return current that leads to power dissipation in the beam just outside the source.
Reduced threshold current in (111)B grown InGaAs∕AlGaAs laser diodes: The positive role of piezoelectric effect
Authors: Deligeorgis G. , Dialynas G. , Hatzopoulos Z. , Pelekanos N. T.
Published: March 2007

The authors demonstrate that (111)B grown InGaAs∕AlGaAs laser diodes outperform their (100) counterparts, in terms of lower threshold currents observed for all temperature and cavity lengths tested. A low temperature threshold current density as low as 15A∕cm2 has been observed in (111)B grown devices, whereas identical (100) laser diodes exhibited threshold in the range of 30–40A∕cm2. The comparison of experimental findings with a Poisson-Schrödinger self-consistent model reveals that the improved performance of the (111)B devices is attributed to the piezoelectric field present in the (111)B In0.1Ga0.9As active quantum well as well as to the different heavy hole effective masses in the (111)B configuration.
Energy and momentum deposition from pulsed optical lattices to nonionized gases
Authors: Ngalande Cedrick , Gimelshein Sergey F. , Shneider Mikhail N.
Published: March 2007

Nonresonant interaction of an optical lattice created by two counterpropagating laser fields with gas molecules is studied with the direct simulation Monte Carlo method. Energy and momentum deposition from lattice to gas in the collision regime are examined and the ability of a lattice to increase gas temperature to thousands of kelvins in a single pulse is shown.
High temperature dielectric study of Cr2O3 in microwave region
Authors: Dube D. C. , Agrawal D. , Agrawal S. , Roy R.
Published: March 2007

A unique cavity perturbation method has been used to study the dielectric behavior of chromium oxide (Cr2O3) in the microwave region at ∼3.5GHz and temperatures up to ∼1100°C. The specimen in the form of pellet was heated by microwave power at 2.45GHz in e-field of a single mode cavity. In the temperature range of measurement, the dielectric constant is found to increase within 10% and loss factor within one and a half times the room temperature values. Results are discussed in the light of agitated ionic motion in the material.
Formation of gold nanoparticles embedded in a polyimide film for nanofloating gate memory
Authors: Kim Jung H. , Baek Kwang H. , Kim Chang Kyung , Kim Young Bae , Yoon Chong Seung
Published: March 2007

A monolayer of vertically aligned Au nanoparticles embedded in a dielectric film was fabricated by sandwiching a 3.4-nm-thick Au film between two polyimide (PI) precursor layers. Au formed uniform-sized nanoparticles on the PI precursor and coalesced into 10nm sized nanoparticles during imidization, forming a well-dispersed monolayer of Au nanoparticles embedded in PI. Capacitance-voltage measurement at 300K showed that the monolayer of Au nanoparticles functioning as a floating gate in Al∕PI∕Au nanoparticles/PI/Si metal-insulator-semiconductor-type capacitor exhibited a capacitance hysteresis of 3.4V at an applied voltage of 6V. The memory effect can be potentially utilized in next generation flash memories.
Simultaneous measurement of potential and dopant atom distributions on wet-prepared Si(111):H surfaces by scanning tunneling microscopy
Authors: Nishizawa M. , Bolotov L. , Kanayama T.
Published: March 2007

The authors demonstrate the ability of scanning tunneling microscopy and spectroscopy to simultaneously measure the distributions of both the surface potential and the individual dopant atoms on the atomically flat hydrogen-terminated Si(111) surfaces prepared by an aqueous NH4F etching without disturbing the original dopant distribution. At the p-n junctions, the acceptor and donor atoms were detected distinctly, and the variation in the observed height reflected the surface potential under the biasing condition. Further, a strong correlation between the dopant fluctuations and the surface potential distributions was identified.
Overlapping resonances and Regge oscillations in the state-to-state integral cross sections of the F+H2 reaction
Authors: Sokolovski D. , De Fazio D. , Cavalli S. , Aquilanti V.
Published: March 2007

A Regge pole analysis is employed to explain the oscillatory patterns observed in numerical simulations of integral cross section for the F+H2(v=0,j=0)→HF(v′=2,j′=0)+H reaction in the translational collision energy range 25–50meV. In this range the integral cross section for the transition, affected by two overlapping resonances, shows nearly sinusoidal oscillations below 38meV and a more structured oscillatory pattern at larger energies. The two types of oscillations are related to the two Regge trajectories which (pseudo) cross near the energy where the resonances are aligned. Simple estimates are given for the periods of the oscillations.
Competing Environmental Management Standards: How ISO 14001 Outnumbered EMAS in Germany, the UK, France, and Sweden
Authors: Bracke Roeland , Albrecht Johan
Published: March 2007

In the middle of the 1990s two international environmental management standards became available for European companies: the European Eco-Management and Audit Scheme (EMAS) and the International Organization for Standardization's ISO 14001. Companies that wanted to implement a standardized environmental management system were confronted with the choice between their national standard, the European standard, or the international one. In the past decennium, the national standards have been abolished and the number of ISO 14001 certified companies has outnumbered the number of EMAS-registered organizations. The speed at which and the extent to which ISO 14001 has outnumbered EMAS differs, however, between countries in the EU-15. We argue that a country classification based on the degree of statism of the collective agency on the one hand, and the degree of corporatism of society's organization on the other, offers a valuable perspective for analyzing the evolution of the uptake of both standards in a country. We present the cases of Germany, the UK, France, and Sweden, and conclude that in countries characterized by a more societal organization of authority, private alternatives for national regulations like ISO 14001 are welcomed and adopted with enthusiasm. In countries characterized by a rather statist organization, such alternatives are looked upon with more suspicion resulting in delayed uptake. Whereas ISO 14001 is a purely private initiative, voluntary registration to the EMAS regulation creates a link between the company and the authorities. In contrast to corporatist settings, this frightens off business participation in associational countries.
Extending HIV/AIDS-Prevention Efforts in Kenya: Primary Schools as Community-Based Organizations
Authors: Luginaah Isaac , Maticka-Tyndale Eleanor , Kairi Wambui , Wildish Janet , Brouillard-Coyle Chris
Published: March 2007

The question of whether primary schools in Kenya can take on community-based activities beyond their day-to-day functioning, emerged from a larger HIV/AIDS education and prevention program—Primary School Action for Better Health (PSABH). The methodology involved both quantitative and qualitative approaches. The quantitative component was based on 163 schools, which were involved in the larger PSABH program. Qualitative analysis was based on consultative meetings with twenty key informants and follow-up focus-group discussions with representatives from eight schools involved in community-based activities. The results suggest that in this context schools have strong community ties, with most of them willing to take up community-based organization (CBO)-related activities beyond their day-to-day functioning. Schools were more likely to take on CBO-related activities, such as support for orphans, if they had a higher proportion of female teachers, a school sponsor that was involved in the selection of the head teacher, more Parent Teacher Association meetings, and if HIV/AIDS was incorporated into community festivals. A school's involvement was reinforced if it performed well in the Kenya Certificate of Primary Education examination, if the school's head teacher was committed, and if most of the teachers were from the local community. Despite several challenges, the findings point to the need to take schools seriously in their duty as CBOs which can have a positive impact in mitigating not only the effects of HIV/AIDS, but also other community-development activities in ravaged sub-Saharan African countries. The proposed expansion of PSABH further puts Kenyan schools in a stronger position to be involved in their communities through CBO-related activities.
Pylons in the Back Yard: Local Planning and Perceived Risks to Health
Authors: Jay Stephen
Published: March 2007

Health fears arising from the presence of high-voltage power lines in residential areas have received recent attention in spatial planning. A study of stances taken by planning authorities in England and Wales shows their willingness to give expression to the concerns of local communities through precautionary measures, and the difficulties encountered in the face of official statements and industry opposition. These attempts to embody local feeling in patterns of development are illustrative of the increasing prevalence of a sense of risk in contemporary society. The spatial patterns of risk are also revealed, which owe much to the presence and distribution of industrial infrastructure in the landscape and to the associated contested use of land.
Cape Town, a Secondary Global City in a Developing Country
Authors: Gibb Matthew
Published: March 2007

In recent years, the concept of the global city has become an important expression primarily used to characterise Western cities that have become key nodes for headquarter functions, financial services, information processing, and other activities that have been undertaken to announce their influence as world leaders. However, this paper parallels recent academic moves to look beyond the North and concludes that global cities also exist in the South. It further introduces Cape Town as a contemporary example of one such city that is becoming more worldly in both appearance and outlook. The city's position as an up-and-coming global city can be accredited to a range of comparative advantages and strategic interventions including successful rejuvenation strategies, gentrification of certain neighbourhoods, a rising number of foreign visitors, and the construction of a world-class international convention facility. While it may not be a top-ranked competitor, Cape Town does display global city characteristics such as a growing aggressiveness on the part of urban planners and development practitioners in foreign investment attraction, strategic marketing campaigns, and the hosting of high-profile events that provide valuable lessons for aspiring secondary global cities.
In Whose Interest? Financial Surveillance and the Circuits of Exception in the War on Terror
Authors: Atia Mona
Published: March 2007

In this paper I argue that discourses of terrorism financing that emerged in the aftermath of the September 11 terrorist attacks encourage the practice of ethnic/religious profiling while categorically delegitimizing and criminalizing Muslim financial networks. In partnership with these discourses are legal and regulatory frameworks that alter accountability parameters for certain classifications of money. Surveillance and monitoring have become sufficiently nuanced, granting the everyday bureaucrat powers of differentiation so as to allow certain money to remain fully mobile while other money is subject to increased tracking and suspicion. The war on terrorism finance is queried as an appropriate tactic in the effort to combat terrorism. I discuss the various facets of the discursive associations forged between terrorism finance hawala wire-transfer services and Islamic charities. Drawing upon Judith Butler's notion of ‘deeming’, I make linkages between discursive associations, sovereignty, and contemporary terrorism prevention practices. Finally, I extend David Harvey's theory of accumulation by dispossession to argue that the frameworks of accountability broadened by the PATRIOT Act and related provisions can be and are being mobilized to seize control of undesirable financial flows and to further US economic interests.
“America is Safe While its Boys and Girls Believe in its Creeds!”: Captain America and American Identity Prior to World War 2
Authors: Dittmer Jason
Published: March 2007

In this paper I engage with the literature on nationalism and popular culture to discuss the role of Captain America Comics in the production of American national identity and national interest prior to World War 2. The character of Captain America is introduced as an example of a rescaling icon, or a bridge between collective identity and the individual. Additionally, the impact of the context in which the comic was produced is discussed as a force in the construction of American identity before the 1941 entry of the United States into the war. The empirical portion of the paper is a content analysis of the first ten issues of Captain America Comics, all predating the attack on Pearl Harbor. The analysis focuses on the ways in which American behavior is disciplined through the narratives in the comic book, as well as the ways in which nationalities are scripted into a moral geography.
Home Extensions in the United Kingdom: Space, Time, and Practice
Authors: Hand Martin , Shove Elizabeth , Southerton Dale
Published: March 2007

This paper begins with two observations: that UK homes appear to have accumulated increasing numbers of domestic technologies, yet new houses are smaller, on average, than those built before 1980. The spatial pressures placed on homes that result from the accumulation of technologies are explored by drawing upon forty household interviews which enquired into the domestic organisation of kitchen and bathroom technologies and practices. Many households have responded to such spatial pressures by extending or reformulating their domestic spaces: such that kitchens are becoming increasingly multifunctional spaces and bathrooms are multiplying. It is argued that these trends are not simply driven by an unstoppable tide of material possession but reflect context-specific arrangements related to the temporal and ideological structuring of domestic practices. Technologies and practices coevolve with the result that new demands are made on homes—the commodities and objects with which we live our lives influence our experience of space and the value placed on different physical configurations. Domestic technologies are therefore implicated in the structure and reproduction of practice and hence in the choreography of things and people in time and space.
Governmentality, Calculation, Territory
Authors: Elden Stuart
Published: March 2007

In this paper I discuss Foucault's two recently published courses, Sécurité, Territoire, Population and Naissance de la Biopolitique. Foucault notes that he has undertaken a genealogy of the modern state and its different apparatuses from the perspective of a history of governmental reason, taking into account society, economy, population, security, and liberty. In the “Governmentality” lecture—the fourth of the first course—Foucault says that the series of the title—that is, security, territory, population—becomes “security, population, government”. In other words, territory is removed and government appended. And, yet, the issue of territory continually emerges only to be repeatedly marginalised, eclipsed, and underplayed. A key concern of the course is the politics of calculation which Foucault discusses through the development of political arithmetic, population statistics, and political economy. Explicitly challenging Foucault's readings of Machiavelli and the Peace of Westphalia, I argue that territorial strategies should themselves be read as calculative, with the same kinds of mechanisms brought to bear on populations applied here too. I therefore discuss how Foucault's discussions of political economy, the police, and calculation are useful in thinking the history of the concept of territory.
A natural history of web decorations in the St Andrew's Cross spider (Argiope keyserlingi)
Authors: Rao Dinesh , Cheng Ken , Herberstein Marie E.
Published: March 2007

A long-running debate in the spider literature concerns the function of the extra silk decorations in some spider webs. These decorations are appended to the web and constitute a highly visible signal, which is inconsistent with the trend towards web invisibility. Despite the sustained attention of researchers, the exact function of these decorations is yet to be understood. While most studies have focussed on testing particular hypotheses, there has been a dearth of natural history data regarding web decorations in field conditions. In this study we present baseline data regarding the influence of seasonality, microhabitat characteristics and ecology on the presence of web decorations in an Australian orb web spider, Argiope keyserlingi. In particular, we show that there is preference among spiders to build their webs between bushes and to face the south-east, but this preference does not influence decoration building.
An explicit counterexample to the equivariant 𝐾=2 conjecture
Authors: Komori Yohei , Matthews Charles
Published: March 2007

We construct an explicit example of a geometrically finite Kleinian group

G
G

with invariant component

Ω
\Omega

in the Riemann sphere

\hat {C}

\textbf {\hat {C}}

such that any quasiconformal map from

Ω
\Omega

to the boundary of the convex hull of

\hat {C}

−
Ω

\textbf {\hat {C}} - \Omega

in

H^3

\textbf {H^3}

which extends to the identity map on their common boundary in

\hat {C}

\textbf {\hat {C}}

, and which is equivariant under the group of Möbius transformations preserving

Ω
\Omega

, must have maximal dilatation

K
>
2.002

K > 2.002

.
IMEx: Imperfect Microsatellite Extractor
Authors: Mudunuri Suresh B. , Nagarajaram Hampapathalu A.
Published: March 2007

Motivation: Microsatellites, also known as simple sequence repeats, are the tandem repeats of nucleotide motifs of the size 1–6 bp found in every genome known so far. Their importance in genomes is well known. Microsatellites are associated with various disease genes, have been used as molecular markers in linkage analysis and DNA fingerprinting studies, and also seem to play an important role in the genome evolution. Therefore, it is of importance to study distribution, enrichment and polymorphism of microsatellites in the genomes of interest. For this, the prerequisite is the availability of a computational tool for extraction of microsatellites (perfect as well as imperfect) and their related information from whole genome sequences. Examination of available tools revealed certain lacunae in them and prompted us to develop a new tool.

Results: In order to efficiently screen genome sequences for microsatellites (perfect as well as imperfect), we developed a new tool called IMEx (Imperfect Microsatellite Extractor). IMEx uses simple string-matching algorithm with sliding window approach to screen DNA sequences for microsatellites and reports the motif, copy number, genomic location, nearby genes, mutational events and many other features useful for in-depth studies. IMEx is more sensitive, efficient and useful than the available widely used tools. IMEx is available in the form of a stand-alone program as well as in the form of a web-server.

Availability: A World Wide Web server and the stand-alone program are available for free access at http://203.197.254.154/IMEX/ or http://www.cdfd.org.in/imex

Contact:  han@cdfd.org.in
N‐terminal domains of native multidomain proteins have the potential to assist de novo folding of their downstream domains in vivo by acting as solubility enhancers
Authors: Kim Chul Woo , Han Kyoung Sim , Ryu Ki‐Sun , Kim Byung Hee , Kim Kyun‐Hwan , Choi Seong Il , Seong Baik L.
Published: March 2007

The fusion of soluble partner to the N terminus of aggregation‐prone polypeptide has been popularly used to overcome the formation of inclusion bodies in the E. coli cytosol.

The chaperone‐like functions of the upstream fusion partner in the artificial multidomain proteins could occur in de novo folding of native multidomain proteins. Here, we show that the N‐terminal domains of three E. coli multidomain proteins such as lysyl‐tRNA synthetase, threonyl‐tRNA synthetase, and aconitase are potent solubility enhancers for various C‐terminal heterologous proteins. The results suggest that the N‐terminal domains could act as solubility enhancers for the folding of their authentic C‐terminal domains in vivo. Tandem repeat of N‐terminal domain or insertion of aspartic residues at the C terminus of the N‐terminal domain also increased the solubility of fusion proteins, suggesting that the solubilizing ability correlates with the size and charge of N‐terminal domains. The solubilizing ability of N‐terminal domains would contribute to the autonomous folding of multidomain proteins in vivo, and based on these results, we propose a model of how N‐terminal domains solubilize their downstream domains.
A quasi‐spontaneous amyloid route in a DNA binding gene regulatory domain: The papillomavirus HPV16 E2 protein
Authors: Wetzler Diana E. , Castaño Eduardo M. , de Prat‐Gay Gonzalo
Published: March 2007

The DNA binding domain of papillomavirus E2 proteins is at the center of the regulation of gene transcription and replication of the virus. Its unique fold consists of a β‐barrel domain that combines an eight‐stranded dimeric β‐barrel core interface with two symmetrical DNA binding α‐helices and other two helices, packed against the central barrel. Treatment with low amounts of trifluoroethanol readily leads to a mostly β‐sheet oligomeric species, with a loss of near‐UV circular dichroism signal and increase in its ANS binding capacity, indicating that buried hydrophobic surfaces become accessible to the solvent. This species subsequently undergoes a slow transition into amyloid aggregates as determined by light scattering and Congo red and thioflavin T binding. Electron microscopy shows short amyloid fibers with a curly aspect as the end product. The amyloid route is completely prevented by addition of stoichiometrical amounts of specific DNA, strongly suggesting that unfolding of the DNA binding α‐helix is required for the formation of the intermediate. The slow nature of this expanded β‐oligomeric species and the availability of several different conformational probes make it an excellent model for investigating amyloid mechanisms. The mild perturbation required for entering an amyloid route is indicative of a preexisting equilibrium. Oligomerization processes are required for the assembly of transcription initiation and DNA replication machineries, where proteins from different viruses must come together with host cell proteins. The E2 protein is a virus‐encoded multifunctional master regulator that may exert one of its multiple functions through its ability to oligomerize.
Structural characterization of the fusion of two pentapeptide repeat proteins, Np275 and Np276, from Nostoc punctiforme: Resurrection of an ancestral protein
Authors: Vetting Matthew W. , Hegde Subray S. , Hazleton Keith Z. , Blanchard John S.
Published: March 2007

The Nostoc punctiforme genes Np275 and Np276 are two adjacently encoded proteins of 98 and 75 amino acids in length and exhibit sequences composed of tandem pentapeptide repeats. The structures of Np275 and a fusion of Np275 and Np276 were determined to 2.1 and 1.5 Å, respectively. The two Nostoc proteins fold as highly symmetric right‐handed quadrilateral β‐helices similar to the mycobacterial protein MfpA implicated in fluoroquinolone resistance and DNA gyrase inhibition. The sequence composition of the intervening coding region and the ability to express a fused protein by removing the stop codon for Np275 suggests Np275 and Np276 were recently part of a larger ancestral pentapeptide repeat protein.
Cytogenetic abnormalities additional to t(11;14) correlate with clinical features in leukaemic presentation of mantle cell lymphoma, and may influence prognosis: a study of 60 cases by FISH
Authors: Parry‐Jones N. , Matutes E. , Morilla R. , Brito‐Babapulle V. , Wotherspoon A. , Swansbury G.J. , Catovsky D.
Published: March 2007

Mantle cell lymphoma (MCL), characterised by t(11;14)(q13;q32), has a poor prognosis. Many cases have additional cytogenetic abnormalities, and often have a complex karyotype. Fluorescence in situ hybridisation (FISH) was used to study 60 cases with leukaemic presentation of MCL, to determine the frequency, clinical correlations and prognostic impact of a panel of molecular cytogenetic abnormalities: 17p13 (TP53 locus), 13q14, 12 p11·1‐q11 (centromere), 6q21 and 11q23. CD38 expression, of prognostic value in chronic lymphocytic leukaemia (CLL), was also studied, and correlations with clinical and cytogenetic abnormalities sought. Eighty per cent of cases had at least one abnormality in addition to t(11;14). Deletions at 17p13 (TP53) and 13q14 were most frequent and involved the majority of the leukaemic clone. Cases with TP53 deletion were more likely to have splenomegaly and marked leucocytosis (>30 × 109/l), and less likely to have lymphadenopathy than those without deletion. Deletions at 11q23 and 6q21 were associated with extranodal disease. 13q14 and 11q23 deletions showed a trend towards worse prognosis by univariate analysis. In multivariate analysis, deletions at 13q14 and 6q21 were independent predictors of poor outcome. Deletion at 17p13 did not show prognostic impact in this series. CD38, positive in two‐thirds of cases, was associated with male gender and nodal disease but not with any cytogenetic abnormality, or with survival.
Chronic graft‐versus‐host disease after allogeneic bone marrow transplantation from an unrelated donor: incidence, risk factors and association with relapse. A report from the Japan Marrow Donor Program
Authors: Ozawa Shinichi , Nakaseko Chiaki , Nishimura Miki , Maruta Atsuo , Cho Ryuko , Ohwada Chikako , Sakamaki Hisashi , Sao Hiroshi , Mori Shin‐ichiro , Okamoto Shinichiro , Miyamura Kouichi , Kato Shunichi , Kawase Takakazu , Morishima Yasuo , Kodera Yoshihisa ,   for the Japan Marrow Donor Program
Published: March 2007

Chronic graft‐versus‐host disease (GVHD) remains the major cause of late morbidity and mortality after allogeneic stem cell transplantation. We retrospectively analysed 2937 patients who underwent bone marrow transplantation from an unrelated donor (UR‐BMT) facilitated by the Japan Marrow Donor Program (JMDP) and survived beyond day 100 after transplantation. The cumulative incidence of chronic GVHD (limited + extensive) or extensive chronic GVHD at 5 years post‐transplant was 45·8% and 28·2%, respectively. On multivariate analysis, seven variables predicting chronic GVHD were identified: recipient age over 20 years, donor age over 30 years, primary diagnosis of chronic myeloid leukaemia, human leucocyte antigen (HLA)‐A or ‐B mismatch, total body irradiation‐containing regimen, platelet count not having reached 50 × 109/l by day 100, and prior acute GVHD. Among 2609 patients with haematological malignancy, overall survival was significantly higher in patients with limited chronic GVHD but lower in patients with extensive chronic GVHD compared with those without chronic GVHD. The cumulative incidence of relapse among patients with limited or extensive chronic GVHD was significantly lower than that among patients without chronic GVHD. Our results suggest that limited chronic GVHD provides a survival benefit to patients with haematological malignancies by reducing the risk of relapse without increasing the risk of death from chronic GVHD.
Efficacy of growth factors compared to other therapies for low‐risk myelodysplastic syndromes
Authors: Golshayan Ali‐Reza , Jin Tao , Maciejewski Jaroslaw , Fu Alex Z. , Bershadsky Boris , Kattan Michael W. , Kalaycio Matt E. , Sekeres Mikkael A.
Published: March 2007

The myelodysplastic syndromes (MDS) represent a heterogeneous group of disorders. Low‐risk MDS represent a subgroup with a relatively good prognosis, but with few trials evaluating outcomes. A pooled analysis based upon a MEDLINE search identified 162 original articles describing patient characteristics and effect of therapy on 2592 individuals with pathologically confirmed refractory anaemia or refractory anaemia with ringed sideroblasts with <5% bone marrow blasts. Treatments were categorised as growth factors (GF) or non‐growth factors (NGF). International Prognostic Scoring System (IPSS) score was documented or calculated when possible. Responses and outcomes were standardised according to the International Working Group MDS criteria. Growth factors produced higher overall response rates (39·5% vs. 31·4% for NGF, P = 0·019), while NGF yielded better CR/PR rates (25·6% vs. 9·1% for GF, P = 0·03). Over 2 years of follow‐up, those receiving GF demonstrated greater overall and progression‐free survival than NGF, after controlling for baseline patient characteristics. Decision tools need to be developed to determine which therapy to choose for patients with low‐risk MDS.
Oncolytic Coxsackievirus A21 as a novel therapy for multiple myeloma
Authors: Au Gough G. , Lincz Lisa F. , Enno Arno , Shafren Darren R.
Published: March 2007

Oncolytic viruses are attractive biological agents for the control of human malignancy. This study assessed the capacity of Coxsackievirus A21 (CVA21) to target and destroy multiple myeloma (MM) and precursor aberrant plasma cells in vitro using established MM cell lines and 15 patient bone marrow (BM) biopsies [n = 10 MM and five monoclonal gammopathy of undetermined significance (MGUS)]. Cell surface analysis revealed that all tumour cells lines expressed high levels of intercellular adhesion molecule‐1 (ICAM‐1) and decay‐accelerating factor (DAF), the receptor molecules to which CVA21 can bind, leading to subsequent cell‐entry and infection. MM cell lines were remarkably susceptible to CVA21 lytic infection, producing 100–1000‐fold increases in viral progeny within 24 h. In contrast, normal peripheral blood cells were refractile to CVA21 infection. Furthermore, challenge of patient BM biopsies with CVA21 for 48 h resulted in specific purging of up to 98·7% of CD138+ plasma cells, with no significant decrease in progenitor cell function. Data generated in this study suggests that CVA21 virotherapy may have potential applications as a systemic anti‐tumour agent for MM, or in the ex vivo purging of malignant plasma cells prior to autologous stem cell transplantation.
Endogenous corticosteroid biosynthesis in subjects after bilateral adrenalectomy
Authors: Freel E. M. , Bernhardt M. , Ingram R. , Wallace A. M. , Fraser R. , Davies E. , Connell J. M. C.
Published: March 2007

Objective  Corticosteroids can be synthesized in extra‐adrenal tissues but the contribution of this to circulating levels in humans is not known. Previous in vitro studies suggest that the ‘hybrid’ corticosteroid 18‐oxocortisol (18‐oxoF) is produced from cortisol by aldosterone synthase. We looked for evidence of extra‐adrenal production of this and other corticosteroids in 10 subjects stable on long‐term glucocorticoid replacement following bilateral adrenalectomy.

Methods  In phase 1, patients were maintained on cortisol alone (30 mg/day), in phase 2 dexamethasone (2 mg/day), and in phase 3, both cortisol and dexamethasone. Each phase lasted 3 days.

Measurements  On the last day of each phase, 24‐h urine collection was performed for analysis of steroid metabolite excretion [using gas chromatography–mass spectrometry (GCMS)] and plasma aldosterone and renin were measured (by radioimmunoassay).

Results  Cortisol metabolite excretion rate [tetrahydrocortisone (THE) + tetrahydrocortisol (THF) + allotetrahydrocortisol (aTHF)] fell from 9169 nmol/24 h in phase 1 to 22 nmol/24 h in phase 2, rising to 6843 nmol/24 h in phase 3. Tetrahydroaldosterone (THAldo) excretion was readily detectable and did not alter significantly between phases (26·5, 23·5 and 28·5 nmol/24 h, respectively; P = 0·474). 18‐Hydroxycortisol (18‐OHF) excretion was easily detectable in phases 1 and 3 (252·5 and 212 nmol/24 h), falling in phase 2 (12 nmol/24 h). 18‐oxoF excretion rates were lower but followed a similar pattern (1·62, 0·085 and 1·785 nmol/24 h in phases 1, 2 and 3, respectively).

Conclusions  Significant levels of adrenal steroids are found in adrenalectomized subjects. We speculate that this occurs at extra‐adrenal sites or in residual adrenal cortex tissue in an ACTH‐independent manner. Our data suggest that aldosterone synthase, acting on cortisol, is the source of 18‐oxoF and 18‐OHF in these subjects. Further studies of corticosteroid production within adrenalectomized subjects, looking for evidence of adrenal regrowth or residual adrenal tissue, are justified.
Free fatty acids inhibit adrenocorticotropin and cortisol secretion stimulated by physical exercise in normal men
Authors: Coiro V. , Casti A. , Rubino P. , Manfredi G. , Maffei M. L. , Melani A. , Saccani Jotti G. , Chiodera P.
Published: March 2007

Background  The basal circulating levels of ACTH and cortisol, but not the ACTH/cortisol response to hCRH, are significantly reduced by free fatty acid (FFA) infusion.

Objective  To verify whether FFA infusion modifies the ACTH/cortisol response to physical exercise, a well‐known activator of the HPA axis at suprapituitary level.

Design  Exercise tests on a bicycle ergometer during infusion of a lipid‐heparin emulsion (LHE) (experimental test) or normal saline (NaCl 0·9%) (control test).

Setting  Department of Cardiology at the University‐Hospital.

Subjects  Seven healthy male subjects aged 25–33 years.

Interventions  On two mornings, at weekly intervals, LHE or saline were infused for 60 min; infusion started 10 min before exercise test on a bicycle ergometer, which lasted about 15 min.

Main outcome measures  Circulating ACTH/cortisol levels and physiological variables during physical exercise.

Results  FFA levels (0·4 ± 0·1 mEq/l) remained constant during control test, whereas they progressively rose (peak at 60 min, 2·7 ± 1·0 mEq/l) during LHE infusion. Neither basal nor exercise‐induced changes in physiological variables were modified by LHE infusion. Both ACTH and cortisol increased during exercise, with peak levels at 20 min and 30 min (control test: 103% and 42%, P < 0·001; experimental test: 28·5% and 18·6%, P < 0·05 higher than baseline, respectively).

Both ACTH and cortisol responses were significantly lower in the experimental than in the control test (at 20 min P < 0·002 and at 30 min P < 0·05 for ACTH; at 20 min P < 0·05 and at 30 min, 40 min and 50 min P < 0·001 for cortisol).

Conclusions  These data represent the first demonstration of an inhibitory action of increased circulating FFA levels on the HPA axis under stimulatory conditions (i.e. physical exercise, a challenge acting at suprapituitary level). In contrast, previous studies did not show FFA effects on the CRH‐induced ACTH/cortisol response. Therefore, our data suggest negative effects of FFAs on the HPA axis at hypothalamic or higher centres in the central nervous system.