bluuebunny/crossref_metadata_2025 huggingface dataset:
Testing Evolutionary Models of Dwarf Irregular Galaxies through Gas and Stellar Metallicity Determinations in HII Galaxies
Authors: Westera Pieter , Cuisinier François , Curty Didier , Buser Roland
Published: March 2013

Dwarf irregular galaxies are usually low-metallicity objects, and show ongoing or very recent star formation, giving rise to their irregular appearance. Especially HII galaxies, a sub-category of dwarf irregulars showing unusually high star formation activity, are believed to be among the least evolved galaxies in existence today. Therefore, they are very interesting objects for studies of early galaxy evolution and of metallicity enrichment mechanisms.

Several groups have developed theoretical evolutionary models of galaxies of this type, describing different possible formation and evolutionary scenarii, and varying factors such as gas infall and outflow, as well as the star formation history, and making predictions about their chemical evolution. One way to evaluate these models is by determining the metallicities of the different components of these galaxies, their gas and stars.

We examine a sample of HII galaxies from the Sloan Digital Sky Survey, which possibly contains the largest homogeneous sample of HII galaxy spectra to date. Using very restrictive selection criteria, which guarantee a sample of high quality spectra and avoid “contamination” by spectra of objects of other nature, we defined a sample of ∼ 700 HII galaxies spectra.

Through emission line strength calibrations and a detailed stellar population synthesis, we determined the metallicities of both the gas and the stellar content of these galaxies.

For HII galaxies up to stellar masses of 5 × 109M⊙, we find enrichment mechanisms not to vary with galactic mass, being the same for low- and high-mass galaxies on average. They do seem to present a greater variety at the high-mass end, though, indicating a more complex assembly history. Our results favour galaxy evolutionary models featuring constantly infalling low-metallicity clouds that retain part of the galactic winds. Above 5 × 109M⊙ stellar mass, the retention of high metallicity gas by the galaxies' gravitational potential dominates.

I would like to thank the Fundação de Amparo à Pesquisa do Estado do São Paulo (FAPESP) for financial support.
Global Dust Budgets of the Magellanic Clouds
Authors: Matsuura Mikako
Published: March 2013

Within galaxies, gas and dust are constantly exchanged between stars and the interstellar medium (ISM). The life-cycle of gas and dust is the key to the evolution of galaxies. Despite its importance, it is has been very difficult to trace the life-cycle of gas and dust via observations. The Spitzer Space Telescope and Herschel Space Observatory have provided a great opportunity to study the life-cycle of the gas and dust in very nearby galaxies, the Magellanic Clouds. AGB stars are more important contributors to the dust budget in the Large Magellanic Cloud (LMC), while in the Small Magellanic Cloud (SMC), SNe are dominant. However, it seems that the current estimates of the total dust production from AGB stars is insufficient to account for dust present in the ISM. Other dust sources are needed, and supernovae are promising sources. Alternatively the time scale of dust lifetime itself needs some revisions, potentially because they could be unevenly distributed in the ISM or clumps.
Gas, Dust and Star Formation in Nearby Galaxies as Seen with the JCMT
Authors: Sánchez-Gallego José Ramón
Published: March 2013

We combine 12CO J = 3 − 2 for 155 nearby galaxies, obtained as part of the James Clerk Maxwell Telescope (JCMT) Nearby Galaxies Legacy Survey (NGLS), with star formation rates derived from Hα luminosities to probe the relation between warm, dense gas and star formation. These data are compared with ancillary data from the literature, including infrared (IR) and 1.4 GHz radio continuum luminosities and Hi masses. We find a good correlation between CO J = 3 − 2 luminosities and Hα-derived star formation rates (SFRs), which is in agreement with previous studies. Several groups of galaxies show a peculiar behaviour in the SFR(Hα) − LCOJ = 3 − 2 plot, which disappears when using IR data. We analyse these regions and propose several hypotheses to explain this behaviour, including group interactions and very recent (≲20 Myr) bursts of star formation only traced by Hα emission. While atomic hydrogen is hardly related with SFR, molecular and total gas (Hi + H2) show similar correlations with Hα luminosities. No correlation is found between CO J = 3−2 luminosity and metallicity, although galaxies with low metallicity are more likely to not be detected. We discuss that CO J = 3 − 2 does not seem to be a significantly better tracer of the star-forming gas, but its independence from metallicity may be used to constrain the conversion factor between CO and H2.
Star Formation Efficiency at Intermediate Redshift
Authors: Combes F. , García-Burillo S. , Braine J. , Schinnerer E. , Walter F. , Colina L.
Published: March 2013

Star formation is evolving very fast in the second half of the Universe, and it is as yet unclear whether this is due to evolving gas content, or evolving star formation efficiency (SFE). We have carried out a survey of ultra-luminous galaxies (ULIRG) between z = 0.2 and 1, to check the gas fraction in this domain of redshift which is still poorly known. Our survey with the IRAM-30m detected 33 galaxies out of 69, and we derive a significant evolution of both the gas fraction and SFE of ULIRGs over the whole period, and in particular a turning point around z = 0.35. The result is sensitive to the CO-to-H2 conversion factor adopted, and both gas fraction and SFE have comparable evolution, when we adopt the low starburst conversion factor of α = 0.8 M⊙ (K km s−1 pc2)−1. Adopting a higher α will increase the role of the gas fraction. Using α = 0.8, the SFE and the gas fraction for z∼0.2-1.0 ULIRGs are found to be significantly higher, by a factor 3, than for local ULIRGs, and are comparable to high redshift ones. We compare this evolution to the expected cosmic H2 abundance and the cosmic star formation history.
A Fundamental Plane for GAMA galaxies
Authors: Lara-López Maritza A. , Hopkins Andrew M. , López-Sánchez Angel R. ,   the GAMA team
Published: March 2013

A full appreciation of the role played by gas metallicity (Z), star-formation rate (SFR), and stellar mass (M*) is fundamental to understanding how galaxies form and evolve. Using data from the SDSS–DR7 and the GAMA surveys we study the Fundamental Plane for star-forming galaxies. Our analysis allows us to confirm the existence of a Fundamental Plane, for which stellar mass = f(Z, SFR) in star-forming galaxies.
Symposium‘The politics of international recognition’
Authors: Agné Hans , Bartelson Jens , Erman Eva , Lindemann Thomas , Herborth Benjamin , Kessler Oliver , Chwaszcza Christine , Fabry Mikulas , Krasner Stephen D.
Published: March 2013

Recognition plays a multifaceted role in international theory. In rarely communicating literatures, the term is invoked to explain creation of new states and international structures; policy choices by state and non-state actors; and normative justifiability, or lack thereof, of foreign and international politics. The purpose of this symposium is to open new possibilities for imagining and studying recognition in international politics by drawing together different strands of research in this area. More specifically, the forum brings new attention to controversies on the creation of states, which has traditionally been a preserve for discussion in International Law, by invoking social theories of recognition that have developed as part of International Relations more recently. It is suggested that broadening imagination across legal and social approaches to recognition provides the resources needed for theories with this object to be of maximal relevance to political practice.
License to kill: is legitimate authority a requirement for just war?
Authors: Reitberger Magnus
Published: March 2013

In traditional just war theory, legitimate authority is regarded as a necessary requirement for war to be just. This article challenges this requirement by arguing that a right to wage war can be derived from the right to self-defense and the justifiability of exercising political power to protect basic human rights. Arguments for the legitimate authority-requirement are then surveyed and rejected as insufficient to defend the principle's privileged status. It is argued that just war theory does not need the legitimate authority-requirement and may benefit from its removal.
The effects of biochar on soil physical properties and winter wheat growth
Authors: Devereux Rachel C. , Sturrock Craig J. , Mooney Sacha J.
Published: March 2013

Biochar has been reported to improve soil quality and crop yield; however, less is known about its effects on the physical and, in particular, structural properties of soil. This study examines the potential ability of biochar to improve water retention and crop growth through a pot trial using biochar concentrations of 0%, 1·5%, 2·5% and 5% w/w. X-ray computed tomography was used to measure soil structure via pore size characteristics; this showed that pore size is significantly affected by biochar concentration. Increasing biochar is associated with decreasing average pore size, which we hypothesise would impact heavily on hydraulic performance. At the end of the experiment, average pore size had decreased from 0·07 mm2 in the 0% biochar soil to 0·046 mm2 in the 5% biochar soil. Increased biochar concentration also significantly decreases saturated hydraulic conductivity and soil bulk density. It was also observed that increased biochar significantly decreases soil water repellency. Increased water retention was also observed at low matric potentials, where it was shown that increased biochar is able to retain more water as the soil dried out. The application of biochar had little effect on short-term (<10 weeks) wheat growth, but did improve water retention through a change in soil porosity, pore size, bulk density and wetting ability.
Chemolithotrophic nitrate-dependent Fe(II)-oxidizing nature of actinobacterial subdivision lineage TM3
Authors: Kanaparthi Dheeraj , Pommerenke Bianca , Casper Peter , Dumont Marc G
Published: March 2013

Anaerobic nitrate-dependent Fe(II) oxidation is widespread in various environments and is known to be performed by both heterotrophic and autotrophic microorganisms. Although Fe(II) oxidation is predominantly biological under acidic conditions, to date most of the studies on nitrate-dependent Fe(II) oxidation were from environments of circumneutral pH. The present study was conducted in Lake Grosse Fuchskuhle, a moderately acidic ecosystem receiving humic acids from an adjacent bog, with the objective of identifying, characterizing and enumerating the microorganisms responsible for this process. The incubations of sediment under chemolithotrophic nitrate-dependent Fe(II)-oxidizing conditions have shown the enrichment of TM3 group of uncultured Actinobacteria. A time-course experiment done on these Actinobacteria showed a consumption of Fe(II) and nitrate in accordance with the expected stoichiometry (1:0.2) required for nitrate-dependent Fe(II) oxidation. Quantifications done by most probable number showed the presence of 1 × 104 autotrophic and 1 × 107 heterotrophic nitrate-dependent Fe(II) oxidizers per gram fresh weight of sediment. The analysis of microbial community by 16S rRNA gene amplicon pyrosequencing showed that these actinobacterial sequences correspond to ∼0.6% of bacterial 16S rRNA gene sequences. Stable isotope probing using 13CO2 was performed with the lake sediment and showed labeling of these Actinobacteria. This indicated that they might be important autotrophs in this environment. Although these Actinobacteria are not dominant members of the sediment microbial community, they could be of functional significance due to their contribution to the regeneration of Fe(III), which has a critical role as an electron acceptor for anaerobic microorganisms mineralizing sediment organic matter. To the best of our knowledge this is the first study to show the autotrophic nitrate-dependent Fe(II)-oxidizing nature of TM3 group of uncultured Actinobacteria.
The benefit of DNA supercoiling during replication
Authors: Schvartzman Jorge B. , Martínez-Robles María-Luisa , Hernández Pablo , Krimer Dora B.
Published: March 2013

DNA topology changes dynamically during DNA replication. Supercoiling, precatenation, catenation and knotting interplay throughout the process that is finely regulated by DNA topoisomerases. In the present article, we provide an overview of theoretical and experimental approaches to understand the interplay between various manifestations of topological constraints acting on replicating DNA molecules. Data discussed reveal that DNA entanglements (supercoils and catenanes) play an active role in preventing the formation of deleterious knots.
Denaturation transition of stretched DNA
Authors: Hanke Andreas
Published: March 2013

In the last two decades, single-molecule force measurements using optical and magnetic tweezers and atomic force spectroscopy have dramatically expanded our knowledge of nucleic acids and proteins. These techniques characterize the force on a biomolecule required to produce a given molecular extension. When stretching long DNA molecules, the observed force–extension relationship exhibits a characteristic plateau at approximately 65 pN where the DNA may be extended to almost twice its B-DNA length with almost no increase in force. In the present review, I describe this transition in terms of the Poland–Scheraga model and summarize recent related studies.
Simple topology: FtsK-directed recombination at the dif site
Authors: Grainge Ian
Published: March 2013

FtsK is a multifunctional protein, which, in Escherichia coli, co-ordinates the essential functions of cell division, DNA unlinking and chromosome segregation. Its C-terminus is a DNA translocase, the fastest yet characterized, which acts as a septum-localized DNA pump. FtsK's C-terminus also interacts with the XerCD site-specific recombinases which act at the dif site, located in the terminus region. The motor domain of FtsK is an active translocase in vitro, and, when incubated with XerCD and a supercoiled plasmid containing two dif sites, recombination occurs to give unlinked circular products. Despite years of research the mechanism for this novel form of topological filter remains unknown.
Small DNA circles as probes of DNA topology
Authors: Bates Andrew D. , Noy Agnes , Piperakis Michael M. , Harris Sarah A. , Maxwell Anthony
Published: March 2013

Small DNA circles can occur in Nature, for example as protein-constrained loops, and can be synthesized by a number of methods. Such small circles provide tractable systems for the study of the structure, thermodynamics and molecular dynamics of closed-circular DNA. In the present article, we review the occurrence and synthesis of small DNA circles, and examine their utility in studying the properties of DNA and DNA–protein interactions. In particular, we highlight the analysis of small circles using atomistic simulations.
Topological constraints and chromosome organization in eukaryotes: a physical point of view
Authors: Rosa Angelo
Published: March 2013

New experimental tools capable of probing the three-dimensional organization of eukaryotic genomes with an unprecedented level of detail have been developed in the last few years. In the quest for a quantitative understanding of experimental results, several polymer models for chromatin organization were introduced and critically evaluated. In the present article, I give a brief introduction to the physical basis of chromosome organization, and recall the experimental evidence in favour of the importance of topological constraints for the description of chromosome conformations in eukaryotes.
Crossing-sign discrimination and knot-reduction for a lattice model of strand passage
Authors: Soteros Chris , Szafron Michael
Published: March 2013

By performing strand-passages on DNA, type II topoisomerases are known to resolve topological constraints that impede normal cellular functions. The full details of this enzyme–DNA interaction mechanism are, however, not completely understood. To better understand this mechanism, researchers have proposed and studied a variety of random polygon models of enzyme-induced strand-passage. In the present article, we review results from one such model having the feature that it is amenable to combinatorial and asymptotic analysis (as polygon length goes to infinity). The polygons studied, called Θ-SAPs, are on the simple-cubic lattice and contain a specific strand-passage structure, called Θ, at a fixed site. Another feature of this model is the availability of Monte Carlo methods that facilitate the estimation of crossing-sign-dependent knot-transition probabilities. From such estimates, it has been possible to investigate how knot-reduction depends on the crossing-sign and the local juxtaposition geometry at the strand-passage site. A strong relationship between knot-reduction and a crossing-sign-dependent crossing-angle has been observed for this model. In the present article, we review these results and present heuristic geometrical arguments to explain this crossing-sign and angle-dependence. Finally, we discuss potential implications for other models of type II topoisomerase action on DNA.
Identifying knots in proteins
Authors: Millett Kenneth C. , Rawdon Eric J. , Stasiak Andrzej , Sułkowska Joanna I.
Published: March 2013

Polypeptide chains form open knots in many proteins. How these knotted proteins fold and finding the evolutionary advantage provided by these knots are among some of the key questions currently being studied in the protein folding field. The detection and identification of protein knots are substantial challenges. Different methods and many variations of them have been employed, but they can give different results for the same protein. In the present article, we review the various knot identification algorithms and compare their relative strengths when applied to the study of knots in proteins. We show that the statistical approach based on the uniform closure method is advantageous in comparison with other methods used to characterize protein knots.
The topology of plasmid-monomerizing Xer site-specific recombination
Authors: Colloms Sean D.
Published: March 2013

Xer site-specific recombination at cer and psi converts bacterial plasmid multimers into monomers so that they can be efficiently segregated to both daughter cells at cell division. Recombination is catalysed by the XerC and XerD recombinases acting at ~30 bp core sites, and is regulated by the action of accessory proteins bound to accessory DNA sequences adjacent to the core sites. Recombination normally occurs only between sites in direct repeat in a negatively supercoiled circular DNA molecule, and yields two circular products linked together in a right-handed four-node catenane with antiparallel sites. These and other topological results are explained by a model in which the accessory DNA sequences are interwrapped around the accessory proteins, trapping three negative supercoils so that strand exchange by the XerC and XerD yields the observed four-node catenane.
Structural insights into the role of architectural proteins in DNA looping deduced from computer simulations
Authors: Olson Wilma K. , Grosner Michael A. , Czapla Luke , Swigon David
Published: March 2013

Bacterial gene expression is regulated by DNA elements that often lie far apart along the genomic sequence, but come close together during genetic processing. The intervening residues form loops, which are organized by the binding of various proteins. For example, the Escherichia coli Lac repressor protein binds DNA operators, separated by 92 or 401 bp, and suppresses the formation of gene products involved in the metabolism of lactose. The system also includes several highly abundant architectural proteins, such as the histone-like (heat-unstable) HU protein, which severely deform the double helix upon binding. In order to gain a better understanding of how the naturally stiff DNA double helix forms the short loops detected in vivo, we have developed new computational methods to study the effects of various non-specific binding proteins on the three-dimensional configurational properties of DNA sequences. The present article surveys the approach that we use to generate ensembles of spatially constrained protein-decorated DNA structures (minicircles and Lac repressor-mediated loops) and presents some of the insights gained from the correspondence between computation and experiment about the potential contributions of architectural and regulatory proteins to DNA looping and gene expression.
Knotting pathways in proteins
Authors: Sułkowska Joanna I. , Noel Jeffrey K. , Ramírez-Sarmiento César A. , Rawdon Eric J. , Millett Kenneth C. , Onuchic José N.
Published: March 2013

Most proteins, in order to perform their biological function, have to fold to a compact native state. The increasing number of knotted and slipknotted proteins identified suggests that proteins are able to manoeuvre around topological barriers during folding. In the present article, we review the current progress in elucidating the knotting process in proteins. Although we concentrate on theoretical approaches, where a knotted topology can be unambiguously detected, comparison with experiments is also reviewed. Numerical simulations suggest that the folding process for small knotted proteins is composed of twisted loop formation and then threading by either slipknot geometries or flipping. As the size of the knotted proteins increases, particularly for more deeply threaded termini, the prevalence of traps in the free energy landscape also increases. Thus, in the case of longer knotted and slipknotted proteins, the folding mechanism is probably supported by chaperones. Overall, results imply that knotted proteins can be folded efficiently and survive evolutionary pressure in order to perform their biological functions.
Framed curves and knotted DNA
Authors: Chirikjian Gregory S.
Published: March 2013

The present mini-review covers the local and global geometry of framed curves and the computation of twist and writhe in knotted DNA circles. Classical inequalities relating the total amount of bending of a closed space curve and associated knot parameters are also explained.
AMPK: opposing the metabolic changes in both tumour cells and inflammatory cells?
Authors: Dandapani Madhumita , Hardie D. Grahame
Published: March 2013

AMPK (AMP-activated protein kinase) is a sensor of cellular energy status that appears to have arisen during early eukaryotic evolution. In the unicellular eukaryote Saccharomyces cerevisiae, the AMPK orthologue is activated by glucose starvation and is required for the switch from glycolysis (fermentation) to oxidative metabolism when glucose runs low. In mammals, rapidly proliferating cells (including tumour cells) and immune cells involved in inflammation both tend to utilize rapid glucose uptake and glycolysis (termed the Warburg effect or aerobic glycolysis) rather than oxidative metabolism to satisfy their high demand for ATP. Since mammalian AMPK, similar to its yeast orthologue, tends to promote the more energy-efficient oxidative metabolism at the expense of glycolysis, it might be expected that drugs that activate AMPK would inhibit cell proliferation and and hence cancer, as well as exerting anti-inflammatory effects. Evidence supporting this view is discussed, including our findings that AMPK is activated by the classic anti-inflammatory drug salicylate.
Mechanisms of microbial escape from phagocyte killing
Authors: Smith Leanne M. , May Robin C.
Published: March 2013

Phagocytosis and phagosome maturation are crucial processes in biology. Phagocytosis and the subsequent digestion of phagocytosed particles occur across a huge diversity of eukaryotes and can be achieved by many different cells within one organism. In parallel, diverse groups of pathogens have evolved mechanisms to avoid killing by phagocytic cells. The present review discusses a key innate immune cell, the macrophage, and highlights the myriad mechanisms microbes have established to escape phagocytic killing.
Decoding the SUMO signal
Authors: Hay Ronald T.
Published: March 2013

SUMO (small ubiquitin-like modifier) emerged from the shadow of the well-established ubiquitin some 15 years ago when it was shown that a distinct conjugation pathway was responsible for SUMO modification. Since then it has been established that SUMO modifies over a thousand substrates and plays diverse roles in many important biological processes. Recognition of SUMO is mediated by short peptide sequences known as SIMs (SUMO-interaction motifs) that allow effector proteins to engage SUMO-modified substrates. Like ubiquitin, SUMO can form polymeric chains, and these chains can be recognized by proteins containing multiple SIMs. One protein that contains such a sequence of SIMs also contains a RING (really interesting new gene) domain that is the hallmark of a ubiquitin E3 ligase. This ubiquitin ligase known as RNF4 (RING finger protein 4) has the unique property that it can recognize SUMO-modified proteins and target them for ubiquitin-mediated proteolysis. Structural and biochemical analyses of RNF4 has shed light on the long sought after mechanism of ubiquitin transfer and illustrates how its RING domain primes the ubiquitin-loaded E2 for catalysis.
Hardware thread‐context switching
Authors: Sawalha L. , Tull M. P. , Barnes R. D.
Published: March 2013

Numerous proposals have advanced fine‐grained thread migration as a mechanism to address power, performance, reliability and memory coherence problems. However, exploiting conventional context switch mechanisms carries significant overhead, limiting the granularity of thread movement. Proposed is a novel hardware context switching circuit that enables low‐overhead hardware thread migration between cores in a single‐chip multiprocessor. This switching circuit supports multiple simultaneous thread switches and can store the context of both currently running and time‐multiplexed threads. The circuit drastically reduces the direct cost of context switches.
Fast solution to nonnegative eigenvalue decomposition for polarimetric SAR
Authors: Liu G. F. , Li M. , Wang Y. J. , Zhang P.
Published: March 2013

Since the iteration solution to the nonnegative eigenvalue decomposition (NNED) is quite time‐consuming, a fast solution to the NNED is proposed. From mathematical theory, a conclusion is derived that the result of the NNED is the maximal of nonnegative real zero roots which ensure that all principal minors are nonnegative. Then, according to the conclusion, the fast solution is proposed of which the main body is calculating zero roots and choosing the zero root which satisfies the conclusion as the result of the NNED. The fast solution is simple; its result is theoretically accurate and its time consumption is much less than that of the iteration solution. Finally, the advantage of the fast solution is demonstrated by the experimental results.
Independent interlayer microfluidic cooling for heterogeneous 3D IC applications
Authors: Zhang Yue , Bakir M. S.
Published: March 2013

Presented for the first time is the implementation of independent microfluidic cooling of different tiers in a 3D stack based on their power dissipation. The impact of this approach on heterogeneous 3D IC stacks, such as memory‐on‐processor and processor‐on‐processor with different power dissipations, has been experimentally explored. The junction temperature difference between tiers with different power dissipation is decreased from 12 to 7°C. Significant junction temperature reduction and thermal decoupling are achieved by this approach compared to air‐cooling.
Target rotation rate estimation via ISAR frame processing
Authors: Huang Yajing , Wang Xuezhi , Li Xiang , Moran B.
Published: March 2013

A method is proposed for estimating the target rotation rate for ISAR imaging based on the frame processing technique. The method utilises the intrinsic structures of the frame which span the Hilbert space of radar return from which the rotational information of the target is extracted. For a prominent point, the intensity of the projection is maximum when the frame component corresponding to the prominent point is built with the target rotation rate.
UWB bandpass filter with notch‐band based on transversal signal‐interaction concepts
Authors: Mirzaee M. , Virdee B. S.
Published: March 2013

Presented is a structure to design a compact ultra‐wideband (UWB) bandpass filter (BPF) with excellent selectivity that enables inclusion of notch‐band characteristics within the filter's passband to mitigate interfering signals that coexist within the UWB spectrum. The proposed filter topology utilises two signal paths with different electrical lengths made up of two wideband BPFs that are connected in parallel. The mechanism of generating notch‐band is delineated based on transversal signal‐interaction concepts. Good agreement is observed between simulated and measured performances of the UWB filter, demonstrating a fractional bandwidth of 123% (2.66–11.2 GHz) with a sharp notch‐band at 5.21 GHz.
Monitoring of ageing chips of semiconductor power modules using eddy current sensor
Authors: Nguyen T.A. , Joubert P.‐Y. , Lefebvre S. , Bontemps S.
Published: March 2013

The relevance of the eddy current sensing technique to monitor the ageing state of electronic power modules has been experimentally studied. To do so, a commercial eddy current sensor was implemented for the evaluation of COOLMOSTM transistor chips soldered on a direct copper bonded ceramic substrate of a power module. The measurement data obtained over a large frequency bandwidth were analysed in the normalised complex impedance plane. The analysis shows that the sensor enables the chip and the substrate to be separately sensed. Furthermore, the ageing state of artificially aged chips can be clearly monitored. These preliminary results allow the design of eddy current micro‐sensors dedicated to power module in‐service monitoring purposes to be envisaged.
Simplified analytical propagation model for railway environments based on uniform theory of diffraction
Authors: He R. , Zhong Z. , Ai B. , Guan K. , Chen R.
Published: March 2013

Proposed is a simplified analytical propagation model in railway environments. A heuristic ray tracing with geometrical optics and uniform theory of diffraction are adopted. Four typical and dominating ray paths that undergo reflections from ground and train roof and diffraction from the corner of the train are considered. The measurements verify that the analytical propagation model works very well in typical railway environments.
Junctionless Π‐gate transistor with indium gallium arsenide channel
Authors: Guo H.X. , Zhang X. , Zhu, Z. , Kong E.Y.J. , Yeo Y.‐C.
Published: March 2013

The fabrication and characterisation of a gate‐first In0.7Ga0.3As channel Π‐gate junctionless transistor by a CMOS‐compatible top‐down approach is reported for the first time. The structure uses a simple layer structure and process flow. 3D device simulation shows that the Π‐gate structure can deplete the channel carriers more effectively compared with planar and tri‐gate devices. The fabricated device with 200 nm gate length shows good transfer characteristics with a Ion/Ioff ratio of ∼104 and subthreshold swing of ∼210 mV/decade. The results indicate the suitability of the proposed structure for junctionless transistor operation.
MIMO‐SAR waveform separation based on inter‐pulse phase modulation and range‐Doppler decouple filtering
Authors: Meng C.‐Z. , Xu J. , Xia X.‐G , Long T. , Mao E.‐K , Yang J. , Peng Y.‐N.
Published: March 2013

The coupling among multiple coded orthogonal waveforms occupying the same frequency band may seriously affect the distributed terrain imaging of multiple‐input and multiple‐output synthetic aperture radar (MIMO‐SAR). Based on the inter‐pulse phase modulation among different transmitting waveforms, a range‐Doppler decouple filtering method is presented to separate waveforms effectively. Finally, numerical experiments are provided to demonstrate the effectiveness of the proposed method.
Multi‐loop coil supporting uniform mutual inductances for free‐positioning WPT
Authors: Kim J. , Son H.‐C. , Park Y.‐J.
Published: March 2013

A planar coil of multiple loops connected in series and in parallel is proposed for wireless power transfer (WPT). The current direction in each loop is mixed in forward and in reverse. The proposed coil gives uniform mutual inductance and enables simple impedance matching for free‐positioning WPT.
Si wire array waveguide grating with parallel star coupler configuration fabricated by ArF excimer immersion lithography
Authors: Okayama H. , Shimura D. , Takahashi H. , Seki M. , Toyama M. , Sano T. , Koshino K. , Yokoyama N. , Ohtsuka M. , Sugiyama A. , Ishitsuka S. , Tsuchizawa T. , Nishi H. , Yamada K. , Yaegashi H. , Horikawa T. , Sasaki H.
Published: March 2013

An Si wire array waveguide grating wavelength demultiplexer fabricated using immersion ArF lithography is reported. The tilt directions of the input and output star couplers are aligned in the same direction to avoid phase error generated at the curved waveguides. A 16 channel device with 200 GHz wavelength spacing was fabricated.
Experimental study on parametric tunable dispersion compensation for WDM channels with mixed OOK and QPSK formats
Authors: Inoue T. , Tanizawa K. , Namiki S.
Published: March 2013

Presented is a parametric tunable dispersion compensation (PTDC) for 43 Gbit/s WDM channels with mixed modulation formats of OOK and QPSK. The residual dispersion for the OOK channels is successfully compensated for, while the QPSK channels with digital coherent detection maintain a good signal quality regardless of various settings of PTDC that involve nonlinear processes of wavelength conversion based on four‐wave mixing. Specific design issues on PTDC are discussed, considering the characteristics of the modulation formats of the received channels.
Quantum cascade laser intensity noise under external feedback conditions estimated from self‐mixing method
Authors: Inoue T. , Tsushima K. , Mori S. , Kasahara K.
Published: March 2013

Measured is the relative intensity noise (RIN) of a mid‐infrared Peltier‐cooled distributed‐feedback (DFB) quantum cascade laser (QCL) with a feedback loop, where optical feedback parameters affecting the RIN were estimated by using the self‐mixing method. To that end, a reflecting mirror forming the external cavity was placed on a voice coil and was moved back and forth after the RIN measurements, by which characteristic waveforms appeared. The amount of external feedback could thereby be deduced. There was no appreciable change in the RIN of the DFB‐QCL, even with an optical feedback being in the coherence collapse regime in the case of conventional DFB‐laser diodes.
Extending dynamic range of RF PWM transmitters
Authors: François B. , Nuyts P.A.J. , Dehaene W. , Reynaert P.
Published: March 2013

A multilevel RF PWM transmitter architecture using power combining is proposed. Multilevel RF PWM is realised by driving one or two power amplifiers with a PWM signal, while the others are turned off or working at full power. By changing the number of amplifiers driven by RF PWM, the duty cycles can be kept out of the pulse swallowing regions, and the dynamic range can be greatly extended. In this way, the advantages of RF PWM can be made available also to standards which require large dynamic ranges, such as the WLAN standard.
70 GSa/s and 51 GHz bandwidth track‐and‐hold amplifier in InP DHBT process
Authors: Deza J. , Ouslimani A. , Konczykowska A. , Kasbari A. , Godin J. , Pailler G.
Published: March 2013

A differential 70 GSa/s track‐and‐hold amplifier has been designed and fabricated in a 320 GHz‐fT InP double heterojunction bipolar transistor process. Measurements show a 51 GHz small‐signal bandwidth with an S11 parameter lower than −15 dB up to 56 GHz. The transient operation is verified up to 70 GSa/s. 60 GSa/s spectral measurements give total harmonic distortion <−46 dB up to 7 GHz and <−37 dB over the whole measurement range.
Design, optimisation, analysis and experimental verification of a new line‐start permanent magnet synchronous shaded‐pole motor
Authors: Shamlou Sadegh , Mirsalim Mojtaba
Published: March 2013

In this study, an optimal design of a new line‐start permanent magnet synchronous shaded‐pole motor (LSPMSSPM) is proposed. A genetic algorithm optimisation method based on transient two‐dimensional finite‐element method (FEM) is applied to reach a global optimum design. Advantages and challenges of the proposed LSPMSSPM are investigated, and its performance characteristics are calculated. Efficiency, power factor, starting behaviour and cost as important key factors are analysed. Finally, FEM results are verified with experimental tests.
Investigation of characteristics of a single‐phase axial flux induction motor using three‐dimensional finite element method and d−q model
Authors: Nasiri‐Gheidari Zahra , Lesani Hamid
Published: March 2013

The aim of this study is to find out the performance characteristics of single‐phase axial flux induction motors. In this study, three‐dimensional time‐stepping finite‐element method is employed to analyse electromagnetic fields. Both eddy current and saturation effects are considered in the simulation. Since this transient solution is a computationally expensive method, a mathematical model based on d−q‐axis theory is presented in this study. Then, the motor's electrical parameters, whose values are requested in the d−q model, are calculated using the analytical method and the DC‐charge test of the built motor. The comparison between experimental and simulation results verifies the success of simulation.
Millimetre‐wave path‐loss variability between two body‐mounted monopole antennas
Authors: Nechayev Yuriy Ivanovich , Wu Xianyue , Constantinou Costas C. , Hall Peter S.
Published: March 2013

Variation of on‐body millimetre‐wave propagation channels with body movements has been studied experimentally. A statistical description of the propagation channel is presented, including path‐loss probability distributions, level‐crossing rates and average fade durations. The median path losses for the considered practical links with omnidirectional monopole antennas lied within the range of 55–88 dB. The signal variation was found to consist of two superimposed variations, in general: the long‐term and short‐term fadings, but was dominated by the much stronger long‐term fading. The use of a simple two‐state Markov process model to describe on‐body communication links is also proposed and its limitations are discussed.
Efficient boundary integral‐resonant mode expansion method implementation for full‐wave analysis of passive devices based on circular waveguides with arbitrary perturbations
Authors: Carceller Carlos , Cogollos Santiago , Soto Pablo , Gil Jordi , Boria Vicente E. , Vicente Carlos , Gimeno Benito
Published: March 2013

In this study, the efficient full‐wave analysis of passive devices composed of circular and arbitrarily‐shaped waveguides is considered. For this purpose, the well‐known boundary integral‐resonant mode expansion (BI–RME) method has been properly extended. Circular waveguides are used for resonant mode expansion, whereas the arbitrary contour is defined by any combination of straight, circular and elliptical segments, thus allowing the exact representation of the most widely used geometries. The proposed algorithm extends previous implementations of the BI–RME method based on circular waveguides by considering circular and elliptical arcs for defining arbitrary geometries. Similarly, it allows the efficient analysis of passive devices based on circular waveguides with arbitrary perturbations, thus providing more accurate results with less computational efforts than a rectangular waveguide‐based BI–RME approach. The extended method has been successfully tested with several practical application examples, having compared its performance with the BI–RME method based on rectangular waveguides.
Dispersion and stability of tricalcium phosphate powders in polyacrylate dispersions
Authors: Tyliszczak Bozena , Sobczak‐Kupiec Agnieszka Lucyna , Bialik‐Wąs Katarzyna , Kuciel Stanislaw
Published: March 2013

Biomaterials is a term used to indicate materials that constitute parts of medical implants, extracorporeal devices, and disposables that have been utilised in medicine, surgery, dentistry and veterinary medicine as well as in every aspect of patient health care. Ceramics biomaterials are used as components of hip implants, dental implants, middle ear implants and heart valves. Porous or particulate calcium phosphate ceramic materials such as tricalcium phosphate (TCP) have proved successful for resorbable hard tissue replacements when low loads are applied to the material. The aim of the present work was to evaluate the biological characteristics of the biomaterial developed. Interactions of TCP with polyacrylate polymers in aqueous dispersions were characterised using X‐ray diffraction, Fourier transform infrared spectroscopy, pH determination and viscosity measurements.
Facile hydrothermal method to synthesise hexagonal rotor‐like cerium carbonate hydroxide and CeO2 nanostructures
Authors: Luo Jingjing , Meng Fanming , Wang Leini , Jiang Yan
Published: March 2013

The hexagonal rotor‐like cerium carbonate hydroxide (CeCO3OH) and CeO2 nanostructures were successfully synthesised via a facile hydrothermal method using Ce(NO3)3 · 6H2O as the cerium resource, HNO3 additive to form an acidic solution, CO(NH2)2 as both precipitator and carbon source and polyvinylpyrrolidone as surfactant. Characterisation techniques using an X‐ray diffractometer, scanning electron microscope, transmission electron microscope, X‐ray photoelectron spectroscopy, thermogravimetric differential thermal analysis apparatus and UV–vis absorption spectrum have been used for studying the roles of Ce(NO3)3 · 6H2O and HNO3. It was found that the amount of Ce(NO3)3 · 6H2O has an obvious effect on the morphology of the as‐synthesised CeCO3OH and CeO2 nanostructures, whereas HNO3 has a significant influence on the crystalline phase. CeO2 has a higher UV absorption than as‐synthesised CeCO3OH, which is likely associated with the charge‐transition between Ce3+ and Ce4+.
Fe3O4–ZnWO4 hybrid microspheres: facile synthesis and magnetically recyclable photocatalytic performance
Authors: Zhou Yu‐Xue , Tong Ling , Chen Xiao‐Bing , Zeng Xiang‐Hua
Published: March 2013

Fe3O4–ZnWO4 composite microspheres with magnetically recyclable photocatalytic performance have been firstly synthesised by a simple refluxing method under mild conditions. The as‐prepared Fe3O4–ZnWO4 composites show good photocatalytic efficiency in degradation of rhodamine B under UV light irradiation and can be recycled five times by magnetic separation without major loss of activity, the magnetic property of Fe3O4–ZnWO4 sample has been studied also. Microspheres show potential use on dye degradation from the solution considering their magnetic recovery properties.
Preparation of in‐situ surface‐modified nanosilica and its application in separating oil from water
Authors: Liu Kai , Zheng Nan , Li Xiaohong , Zhang Zhijun
Published: March 2013

A report is presented on the preparation of surface‐functionalised nanosilica from silicon tetrachloride (SiCl4, one of the major by‐products in the polycrystalline silicon industry) by in‐situ surface modification in aqueous solution. The approach uses both SiCl4 and sodium metasilicate as the silicon sources to generate nanosilica, whereas the proportion of sodium metasilicate and SiCl4 is adjusted to control the pH value of the reaction system. In this way, desired SiO2 nanoparticles were in‐situ surface‐modified by hexamethyldisilazane as soon as they were generated in the reaction solution, which makes it feasible to prevent the severe aggregation of nanosilica that often happens during the hydrolytic process. The obtained nanosilica with uniform particle size distribution (mean diameter 35–40 nm) shows superhydrophobicity (a water contact angle of 165°) and excellent organic dispersibility. Thanks to the low cost of raw materials as well as the superhydrophobicity and lipophilicity of as‐prepared nanosilica, its application for improving the selective penetration of oil is primarily investigated. The result shows that quartz sand modified by as‐prepared nanosilica can separate diesel oil from water successfully, which could be significant for improving crude oil recovery efficiency.
Nanoimprinting of TiO2–SiO2 photocurable materials with high titanium concentration for CF4/O2 etch selectivity
Authors: Takei Satoshi
Published: March 2013

The nanofabrication of nanometre‐scale multiple‐level structures by nanoimprint lithography and CF4/O2 etching rates was investigated for nanoelectro mechanical systems and three‐dimensional (3D) wafer‐level packaging. A TiO2–SiO2 sol–gel photocurable material with high titanium concentration of 20.9 wt% was developed for CF4/O2 etch selectivity with a pattern transferring carbon layer in a bi‐layer process. The nanostructures of 3D micropatterns, holes with 200 nm diameter and 130 nm‐wide dense lines with line edge roughness of ∼10 nm were provided. The CF4/O2 etching rate of the TiO2–SiO2 photocurable material was ∼3.7 times lower than that of the referenced SiO2 sol–gel photocurable material. The CF4/O2 etch rates of titanium‐based photocurable materials were confirmed for deep plasma etching processes.
Magnetic stability of ultrathin FeRh films
Authors: Han G. C. , Qiu J. J. , Yap Q. J. , Luo P. , Laughlin D. E. , Zhu J. G. , Kanbe T. , Shige T.
Published: March 2013

This paper presents magnetic properties of highly ordered ultrathin FeRh films deposited on Si/SiO wafers with MgO as a buffer layer. The antiferromagnetic to ferromagnetic (FM) transition is observed with a thickness as low as 3 nm. However, as the thickness decreases, the residual magnetization (Mrs) at low temperature increases and the amplitude of the transition decreases. In addition, the transition becomes much broader for the thinner films. This broadening is related to the grain size reduction in the thinner films. The temperature dependence of the magnetization of a highly ordered B2 FeRh film with a thickness of 10 nm was carefully measured as a function of field. The results show that the transition temperature decreases almost linearly with a rate of 0.93 K/kOe (heating) and 0.97 K/kOe (cooling) close to the value for the bulk samples, while Mrs obtained at 100 K increases rapidly at low field and then linearly at a field larger than 10 kOe, which clearly demonstrates that an applied field would induce FM stabilization in ultrathin FeRh films.
(001) oriented L10 FePt/B4C multilayer thin films on naturally oxidized Si substrate
Authors: Zhang J. , Ding H. , Li S. Q. , Li Q. T. , Wang H. B. , Mo Q. , Wang H.
Published: March 2013

(001) oriented FePt/B4C multilayer thin films with high perpendicular coercivity (≥9.7 kOe) were prepared on naturally oxidized Si substrates by magnetron sputtering and thereafter annealing. Effect of FePt layer thickness on the texture parameter of the (001) orientation, chemical ordering, and magnetic properties has been studied. It was found that the texture parameter of (001) orientation increases while the degree of chemical ordering decreases with the decrease of FePt layer thickness. The coercivity drops with the decrease of layer thickness due to the low degree of chemical ordering. The results of δM plots analysis show that intergrain exchange coupling action weakens in response to the decrease of layer thickness and thus decreases the remanence ratio.